2009
2. Introduction
3. Cooking Fire Loss Statistics
4. Residential Ranges in Canada
5. 2005-2006 Ontario Stovetop Fire Survey
7. Stovetop Fire Mitigation Technologies
9. Conclusions
10. Recommendations
Appendix B: Fire Safety Concepts Tree
Appendix C: 2005-2006 Stovetop Fire Survey
Appendix D: Public Education Resources to Prevent Cooking-related Fires
In the last decade, cooking equipment was identified by the Office of the Fire Marshal’s (OFM) fire loss reporting system as the number one ignition source, accounting for one in four preventable home fires in Ontario. It was also the leading reported ignition source attributed to home fire injuries and the second leading ignition source attributed to home fire deaths. Recognizing this, the Ontario Fire Marshal’s Public Fire Safety Council established the Stovetop Technical Subcommittee to examine stovetop fires and to develop and implement stovetop fire prevention strategies.
Electric powered ranges are currently used in nearly 91% of all households. The remaining households use ranges that are fuelled predominantly by natural gas. Electric ranges can be further subdivided into two main categories, namely those equipped with conventional coil elements and smoothtop models. Although coil ranges are found in the vast majority of homes, smoothtop ranges have been gaining significant market share in recent years.
To gain further insight into the nature of stovetop fires, the OFM developed the Ontario Stovetop Fire Survey. This survey was distributed to fire departments to gather information on all stovetop fires they attended within a one-year period. An analysis of the survey results generated the following key findings:
An analysis of stovetop fire fatalities from 1995 to 2004 resulted in the following key findings:
Various stovetop fire mitigation technologies have been introduced in recent years to provide an alternative approach to reducing stovetop fires. In 2001, the consultant, Arthur D. Little conducted an evaluation of 22 different technology classes that were available at that time. The study concluded that the following technology categories had the highest potential:
The aforementioned technology categories are generally consistent with the strategies derived from the National Fire Protection Association’s (NFPA) Fire Safety Concepts Tree analysis, which is a useful tool for evaluating how an overall objective such as mitigating stovetop fires can be achieved. Applying this tool to stovetop fires identified the following as being potentially effective strategies for preventing or managing these fires:
As part of the subcommittee’s work, the OFM conducted demonstrations regarding possible ignition scenarios using an electric coil range versus a smoothtop range. It was determined that smoothtops had a distinct advantage over coil elements with respect to mitigating clothing ignition through direct contact with the element set at “maximum” power. However, no significant difference between the two could be established with respect to preventing oil ignition in an unattended cooking scenario. Demonstrations also revealed that clothing ignition can occur at power settings just below “maximum” levels for both range types.
A literature review on the cost of deaths and injuries in combination with recent fire loss statistics revealed that stovetop fires cost Ontarians an estimated $48 million annually.
The following key recommendations are presented to reduce fatalities and serious injuries that originate from stovetop fires in Ontario:
In the last decade, cooking equipment 1 was identified by the Office of the Fire Marshal’s (OFM) fire loss reporting system as the number one ignition source, accounting for one in four preventable home fires in Ontario. It was also the leading reported ignition source attributed to home fire injuries and the second leading ignition source attributed to home fire deaths. Fires that originate on the stovetop are of primary concern as they account for the vast majority of all cooking equipment fires. This theme is generally consistent throughout other parts of Canada as well as in other countries around the world.
In recognition of these concerns, the Ontario Fire Marshal’s Public Fire Safety Council established the Stovetop Technical Subcommittee to gain a better understanding of the stovetop fire problem. The Stovetop Technical Subcommittee consists of representatives from the fire service, Electrical Safety Authority (ESA), Canadian Standards Association (CSA), Underwriters Laboratories Canada (ULC), Health Canada, Canadian Appliance Manufacturers Association (CAMA), along with the Office of the Fire Marshal (OFM).
To gain further insight into the nature and extent of stovetop fires, the Subcommittee gathered information to address the following questions:
The Stovetop Technical Subcommittee agreed that a thorough understanding of the stovetop fire problem would better assist them with the development and implementation of effective prevention strategies.
A review of fire losses for the 10-year period between 1998 and 2007 revealed that Ontario averaged approximately 6,046 preventable home fires annually.2 During this period, cooking equipment was identified as the leading ignition source attributed to preventable home fires, averaging 1,494 cooking equipment fires annually or 24% of all preventable home fires.
Figure 1: Preventable Residential Fires-Ignition Source 1998 to
2007
The OFM fire loss reporting system identified cooking equipment as the leading ignition source associated with preventable home injuries, accounting for an annual average of 184 injuries between 2003 and 2007. With an annual average of six fatalities, cooking equipment was the second leading ignition source associated with preventable residential fire fatalities during this five-year period. These fires resulted in an average loss of $23.1 million annually.
Figure 2: Ontario Preventable Residential Fires 2003 to 2007 -
Average # of Injuries and Fatalities per year
The vast majority of cooking equipment related fire losses originated on the stovetop. Between 1998 and 2007, 74% of total cooking related fires were attributed to stovetops. In the five-year period between 2003 and 2007, Ontario averaged 986 stovetop related fires that resulted in five deaths, 155 injuries and $17.6 million in property losses annually. Nearly 47% of cooking related deaths was attributed to the ignition of clothing.
There has been much progress made in the reduction of stovetop fires in the last decade as occurrences have declined 32% over this period. Despite this, it is recognized that stovetops are still the leading factor associated with preventable, residential fires and there is considerable room for improvement.
Although the preceding statistical analysis relates only to the Province of Ontario, clearly the cooking fire problem extends well beyond provincial boundaries. It exists throughout Canada as well as in all other countries that use cooking appliances. In other words, losses due to cooking fires are a global problem. The following is a synopsis of the stovetop fire problem experienced in other jurisdictions.
Canada
The following table summarizes recently reported cooking equipment related fire losses within Canada. These totals were compiled from the latest “Fire Losses in Canada” annual reports published by the Council of Canadian Fire Marshals and Fire Commisioners.3 The number in parenthesis represents cooking equipment as an overall percentage of all ignition sources.
| Year | No. of Fires | Injuries | Deaths | Dollar Loss |
|---|---|---|---|---|
| 1998 | 6,230 (10.8%) |
603 (22.4%) |
31 (9.2%) |
$69.9 M (5.9%) |
| 1999 | 6,143 (11.1%) |
493 (21.6%) |
34 (8.8%) |
$76.1 M (6.2%) |
| 2000 | 5,527 (10.3%) |
510 (20.5%) |
32 (9.8%) |
$69.2 M (5.8%) |
| 2001 | 5,625 (10.2%) |
492 (21.3%) |
41 (12.1%) |
$87.7 M (6.2%) |
| 2002 | 5,541 (10.3%) |
557 (21.9%) |
17 (5.6%) |
$81.7 M (5.5%) |
| Average | 5,813 (10.5%) |
531 21.5%) |
31 (9.1%) |
76.9 M (5.9%) |
| Overall Rank | 2 | 2 | 2 | 4 |
In comparison to other ignition sources, cooking equipment is the second leading cause of fires, injuries and deaths behind “smokers’ material and open flame” and the fourth leading cause of dollar losses in Canada.
It is noteworthy that these totals represent all cooking equipment related fires, including those that occurred in non-residential buildings. Residential fire loss data sorted by ignition source are unavailable at the federal level. However, a survey of various provinces in Canada indicates that approximately 90% of all cooking fires originate in the home.2,4 Due to the inclusion of non-residential data, the actual totals for residential fire losses are expected to be slightly less than those in Table 1. However, the overall loss percentages would be significantly higher by excluding non-residential data.
United States
According to the American-based National Fire Protection Association’s (NFPA) study, “Home Fires Involving Cooking Equipment”, cooking equipment was involved in an estimated 146,000 “reported” U.S. home structure fires in 2005, accounting for 40% of total home fires.5
These fires resulted in an estimated 4,690 civilian injuries, 480 civilian deaths, and $876 million in property losses. In addition, the report estimated that cooking fires accounted for another 12.3 million “unreported” home fires annually, which represents 55.3% of all unreported fires. Although the vast majority of these “unreported” fires resulted in no dollar loss, the study estimated that this translated into an additional 642,000 injury cases per year. This estimate represents 140 times the number of reported home cooking related injuries. While this research is based on an estimate of the differences between reported and unreported fires, it can be used as an indicator of how large the problem is.
In 1999, the U.S. began compiling statistics on the numbers of cooking fires that remained confined to the pan through the use of a new fire statistics reporting form (NFIRS 5.0). Between 1999 and 2005 an average of 71% of total cooking fires were reported to have been confined to the pan. These confined fires accounted for 32% of total cooking related injuries, 4.4% of direct property loss and 0% of deaths.
| Year | No. of Fires | Civilian Deaths | Civilian Injuries | Direct Property Damage as Reported |
|---|---|---|---|---|
| 1999 |
84,100 (37,400) |
310 (310) |
2,600 (1,710) |
$512
M
($484 M) |
| 2000 |
69,800 (22,300) |
240
(240) |
3,020 (2,040) |
$521
M ($479 M) |
| 2001 |
121,200 (38,900) |
500 (500) |
4,400 (2,930) |
$531
M ($508 M) |
| 2002 |
206,800 (61,400) |
150
(150) |
4,900
(3,340) |
$680
M ($653 M) |
| 2003 |
143,600 (35,900) |
520 (520) |
4,480
(3,080) |
$770
M
($740 M) |
| 2004 |
150,600 (36,100) |
620 (620) |
4,820 (3,310) |
$725
M
($699 M) |
| 2005 |
146,400 (37,600) |
480 (480) |
4,690 (3,300) |
$876
M ($845 M) |
| Average |
131,785 (38,514) |
403 (403) |
4,130 (2,816) |
$659
M ($630 M) |
Note: Numbers in parentheses exclude confined fires. Confined fires are reported as confined to a cooking vessel and involving cooking equipment.
The cooking range was involved in 68% of all home cooking fires. The number one factor contributing to these fires is “equipment unattended”, which represents 38% of home cooking fires. In another study conducted by the U.S. Consumer Products Safety Commission (CPSC), involving follow-up investigations of range fires attended by the fire service, it was determined that 58% of range related fires started in unattended situations.6 This figure is more in line with what is currently being experienced in Ontario.
Finally, the aforementioned NFPA study concluded that households using electric ranges have higher rates of fire incidents (47%), civilian injuries (118%) and direct property damage (133%) when compared to those that use gas ranges. On the other hand, gas ranges are riskier when it comes to civilian deaths (15%).
United Kingdom
According to a 2004 report published by the United Kingdom Office of the Deputy Prime Minister, cooking appliances is the leading ignition source responsible for accidental dwelling fires.7 During that year, this ignition source accounted for 57% (27,200) of all accidental dwelling fires and resulted in 54% (5,377) of injuries and 16% (52) of deaths. “Chip/fat pan fires” is one of the causes tracked in the U.K. fire loss reporting system. This category accounted for 15% (7,400) of accidental dwelling fires that resulted in 26% (2614) of the injuries and 10% (32) of the fatalities.
New Zealand
According to the New Zealand Fire Service, in 2005, the country experienced 912 residential cooking equipment fires, which represents 21% of total fires reported in the home.8 “Stove, cook top unit, range top” were involved in 72% of cooking equipment fires.
In another study conducted by the New Zealand Fire Service Commission, between 1991 and 1997, 14% of unintentional domestic fire deaths were linked to a stovetop or an oven.9 The vast majority (93%) of these fatalities were attributed to the ignition of food that was left on the stovetop. The number of fatal fire incidents caused by abandoned cooking materials has been relatively constant over time.
According to 2006 market data provided by CAMA cooking ranges can be found in 99% of the 12.7 million households across Canada.10 Electric powered stovetops are predominantly used in these households, accounting for 91.1% market saturation of households, whereas natural gas fuelled stovetops account for approximately 8%. Ontario’s market data is similar with a household saturation rate of 86.9% for electric range versus 12.3% for gas ranges.
Electric stovetops are divided into two categories: those equipped with conventional electric coil heating elements and the more recently introduced smoothtop (also called “Ceran” top) models. Although coil ranges are generally found in the vast majority of homes, the smoothtop ranges have been gaining significant market share in recent years. According to 2008 CAMA data, electric smoothtop ranges accounted for 57% of total sales of ranges in Canada. Electric coil and gas ranges accounted for 34% and 9% of total sales respectively.
The Canadian Electrical Code (CEC) requires that electric-powered ranges for domestic use in Canada meet the construction requirements of the standard CAN/CSA-C22.2, No. 61-Household Cooking Ranges.
The Ontario Technical Standards Safety Act requires that domestic gas powered ranges be approved to an appropriate construction standard applicable to such an appliance. The ANSI Z21.1-Household Cooking Gas Appliances standard is one commonly used by natural gas-fuelled range manufacturers.
The stovetop is designed such that the elements operate at the selected temperature to heat the cookware, which in turn cooks the food. Demonstrations undertaken by the OFM have shown that electric coil elements can reach temperatures in excess of 700 C, whereas smoothtops attain a lower cooking surface temperature of approximately 500 C.28 Natural gas elements can produce an open flame that reaches a temperature of nearly 600 C.
These element temperatures can far exceed the ignition temperature of household materials typically found around the kitchen. When these materials are heated beyond their respective ignition temperatures or inadvertently come in contact with a hot element, ignition occurs.
| Typical Materials | Ignition Temperatures (C) |
|---|---|
| Cooking oils (corn, olive, cotton seed, palm, peanut, soybean) | 316-445 |
| Natural Cellulosic Fibers (cotton, hemp, jute, linen, sisal, etc.) | 255-400 |
| Natural Protein Fibers (wool, mohair, cashmere, camel hair, etc.) | 570-600 |
| Plastics | 416-580 |
| Rubber | 260-316 |
| Paper | 218-246 |
| Various woods | 190-260 |
Incidents involving the ignition of oil, grease and other food items represent the vast majority of cooking fire scenarios. The aforementioned U.S. Consumer Products Safety Commission range fires study estimated that in cooking oil and other food ignition scenarios, two-thirds of these incidents occurred within the first 15 minutes of cooking. The oil ignition time can be further reduced when reused cooking oils are involved. Heating reused oil leads to degradation and an increase in the free fatty acid content and results in a reduction in its smoke, fire and ignition temperatures. Therefore the more the oil is reused, the greater the fire risk.
Electric stovetop oil ignition demonstrations undertaken by the OFM have shown that ignition times vary based on a number of parameters including oil volume.30 In a demonstration involving 50mL of oil in a pan heated at the “maximum” power setting, ignition occurred in less than four minutes. Ignition times involving larger quantities of oil (250 and 500mL) heated in appropriate sized pots ranged from 10 to 16 minutes. A relative comparison between coil and smoothtop ranges revealed that there were no significant differences in oil ignition times between the two types of stovetops. It should be recognized that these ignition times may vary depending on the pan material, thickness, design and ambient conditions.
A separate demonstration involving the ignition of clothing materials (cotton, polyester and cotton/polyester blend) through direct contact with the elements was also conducted.30 It was determined that the coil elements at the “maximum” setting ignited the material samples immediately upon contact. In contrast, it took the smoothtop elements several seconds to ignite the cotton and cotton/polyester blend materials. The smoothtop was unable to ignite the polyester material within the demonstration’s 30-second time parameters.
Further demonstrations were conducted to study how elements set below their “maximum” settings impact the ignition of cotton and cotton/polyester blend materials.28 It was revealed that the materials ignited within 30 seconds with the coil element set at Levels 7 and 8 (out of nine settings). Similarly, the materials ignited within 30 seconds with the smoothtop element, set at Level 6 (out of seven settings).
Although a smoothtop element will not necessarily prevent the ignition of clothing that comes in contact with it, the additional ignition lag time it has over a coil element provides the user with a window of opportunity to either complete the task at hand (i.e. reaching over an element) or recognize/react to the situation to prevent ignition.
The Ontario Stovetop Fire Survey was developed by the OFM in consultation with industry stakeholders to gain further insight into the nature and extent of stovetop fires. The survey posed questions on residence information, stove/element details, extent of fire spread, type of cooking, and details relating to occupant characteristics and behaviour. A copy of the survey is provided in Appendix B.
This survey was distributed to fire departments throughout the province for completion. Fire department suppression staff was requested to complete the survey for every residential stovetop fire they responded to for a one year period from August 1, 2005 to July 31, 2006.
At the end of this period, 1,244 surveys were completed by the fire service. Fire losses reported included 205 injuries, one death and $10.2 million in property damage. Although the response rate was high, these numbers do not represent all stovetop fires that occurred in Ontario during this period.
The following are the key findings obtained through the analysis of this data:
Figure 4: Stovetop fires by time of day
Figure 5: Object first ignited
27%-pan frying
23%-deep fat frying and
23%-simmering in pot (e.g. soup, sauces, etc.)
The survey asked the fire department to report the key factor contributing to the ignition or spread of fire.
Figure 6: Key factor contributing to ignition or spread of fire
Figure 7: Fires per million population by age group
Figure 8: Smoke alarm presence and operation in stovetop fires.
|
Occupant method of extinguishment |
Injury Rate
(per 100 fires) |
%
Using method of extinguishment |
|---|---|---|
| smothered with lid, chemical, or cloth | 13 | 27 |
| moved pot | 30 | 19 |
| water | 20 | 30 |
| fire extinguisher | 14 | 17 |
During the survey period the OFM investigated seven stovetop fire fatalities. Due to this limited sample size, a larger 10-year analysis was performed using OFM investigation reports.
Most stovetop fires are preventable as they are almost always caused by human behaviour. The impacts of stovetop fires range from minor inconvenience to injury and even death. The fatality rate per 1,000 fires is lower than other residential fires, but the injury rate is significantly higher.
There are specific population groups that are at greater risk. The incident rate of stovetop fires is highest in the 20 to 30 years age group, while the risk of fatality is greatest among older adults (65 years +).
Injuries, deaths and losses resulting from stovetop fires can be reduced through effective public education that targets these populations, and raises awareness about safe cooking practices.
The Fire Safety Concepts Tree is a visual tool developed by the NFPA to assist fire safety practitioners (e.g. designers, engineers, code officials) with communicating fire safety and protection concepts.15 It uses a hierarchal structure to describe how a high-level fire safety objective can be achieved by accomplishing a combination of multiple level sub-objectives.
This is a useful tool for evaluating how an overall objective such as mitigating stovetop fires can be achieved. It can also be effectively used to identify where new stovetop fire mitigation technologies and public education strategies should be directed.
An explanation of the fundamental concepts of the Fire Safety Concepts Tree is provided in Appendix B.
Applying the Fire Safety Concepts Tree to stovetop fires highlights potentially effective strategies for mitigating the stovetop fires problem. This exercise also eliminates certain approaches that are impractical for such an application. In summary, the following strategies are identified as being the most effective options for mitigating stovetop fires:
Figure 9: Fire Safety Concepts Tree for Stovetop Fires
The Ontario Stovetop Fire Survey results clearly indicate that occupant behaviour plays a significant role with respect to cooking-related fires. Although enhanced public education programs have been effective in reducing losses over the years, it is recognized that it is difficult to reach all high-risk groups and to ensure that everyone within those groups are effectively educated about cooking fire prevention.
The use of new technologies specifically designed to mitigate these types of fires is a potentially effective approach for complementing public education programs. Stovetop fire mitigation technologies effectively “engineer out” the problem irrespective of occupant behaviour.
Since the mid-1990s, the U.S. Consumer Products Safety Commission (CPSC) has sponsored work to study developing technology that has the potential to reduce the risk of stovetop fires. CPSC engaged the National Institute of Standards and Technology (NIST) to conduct early phases of this work.
The CPSC in conjunction with the Association of Home Appliance Manufacturers (AHAM) engaged the consultant Arthur D. Little to conduct a study to evaluate the technical, practical and manufacturing feasibility of 22 classes of range technologies intended to address the ignition of cooking materials. The findings were presented in a May 2001 report, “Technical, Practical and Manufacturing Feasibility of Technologies to Address Surface Cooking Fires”.16
In the meantime, companies have continued to develop new products to address surface cooking fires. Some of these concepts involve the use of automatic extinguishing systems, fire separations around the stove to contain a fire, motion sensors to prevent unattended cooking and other sensors that monitor and control heat input.
One of the major areas to consider with any evaluation of mitigation techniques that are tied to the electric range is the average useful life of this appliance. Information provided by the Association of Home Appliance Manufacturers (AHAM) and Natural Resources Canada data show that electric ranges have an average lifespan of approximately 18 to 22 years.31,32 Any technical solution built into the range will need to consider the lifespan of the range in order that the safety mechanism not fail before the range’s end of life. The range’s long lifespan also means that it will take many years for any new built-in technology to be fully integrated into homes.
Currently, hundreds of stovetop mitigation technologies are in existence as consumer products or patents. Little evaluated products that utilize these technologies by developing screening criteria that rated the following categories:
Numerical scores were totaled based on a rating scale of “High”, “Medium” or “Low” assigned to each category. Technologies that were effective in mitigating surface cooking fires with limited impact on other aspects of the product were earmarked to warrant further detailed evaluation. The following categories of technology were identified as having the highest potential and warranting further detailed study.
This technology involves detecting the presence of a fire and activating a fire extinguishing system. A fusible link or temperature sensor (thermocouple, diode or thermistor) located above the cooktop activates the extinguishing system. Some systems incorporate a combination of both smoke and temperature sensors to determine the presence of a cooking fire. The extinguishing agent can be liquid or powder. The system can be combined to include the actuation of an alarm or power source cut-off.
This technology is intended to ensure that a person is present when the cooktop is being used. It uses a motion sensor located at the front of the appliance to detect the presence of a user nearby. The system sounds an alarm if no one is detected after a defined period of time. The user can reset the stove without any effect on the cooking process. A variation of this concept includes a control component that can reduce the heat input or power off if no one responds to the alarm. Another variation adds a pan contact temperature or power sensor that actuates the motion sensor only when the stove’s power level or pan temperature exceeds a pre-set level. Hence, a person does not have to be present unless the pan temperature is nearing pre-ignition levels.
This technology is another variation on the previous concept with the exception that it does not use a motion sensor. Instead, an alarm will activate based on the power level selected and a timer that initiates after the stove has been turned on. When the alarm is triggered, the user can reset it to establish user presence around the cooktop or the control will power off.
This technology was added to Little’s list even though it did not score well in their evaluation due to its incompatibility with electric smoothtop ranges. The reason for its inclusion is due to the fact that there had already been a significant amount of work conducted on this technology, and cooking products manufactured and sold in Japan currently use this approach.
This technology monitors the pan temperature and prevents the pan contents from igniting. It combines a pan bottom temperature sensor with electrical/mechanical controls to prevent content temperatures from rising to the ignition level. The temperature is monitored with a thermocouple or IR sensor and controls adjust the heat input to limit maximum temperatures.
In 2004 the American National Standards Institute (ANSI)/Underwriters Laboratories (UL) Standards Technical Panel No. 858, which included representatives from CSA, developed Technical Feasibility Performance Goals (TFPG) to evaluate cooking fire mitigation techniques for ranges.29 The TFPG provides guidance to designers of devices that could be incorporated into an element/burner and that would interface with a cooking vessel to sense an over temperature condition. Any new technologies designed based on this principle should consider this TFPG.
Finally, a variation on this “Prevent Ignition in Pan” concept involves thermostatically controlled heating elements that limit operating temperatures. One such product that is currently available on the market permits electric coil stoves to be retrofitted with elements that limit cooking temperatures to 350 C. This safeguard prevents the ignition of an unattended pot of oil left on the stovetop.
Induction cooktops were not one of the products reviewed in the Little report. Nevertheless, this is a relatively new technology that is worthy of consideration due to its increasing acceptance in Japan and Europe, since its introduction in the early 1990s.
Induction cooktops incorporate electromagnetic technology to permit the user to cook food safely, quickly, and efficiently. The appliance directly heats up the cookware with magnetic fields rather than relying on a hot or open flame element. This allows the cooking surface to remain relatively cool to the touch, reducing burn and ignition of nearby combustible scenarios generally associated with conventional cooking appliances. In addition, some models incorporate built-in safety features such as an auto-shutoff if it detects that there is no cookware placed on the cooking surface or if there is an abnormal rise in cookware temperature generally associated with heating an empty pot.
Implementing the aforementioned technologies may be an effective means of reducing stovetop fires because it eliminates the human behaviour factors that contribute to these incidents. However, each technology requires evaluation in combination with the cooking appliance and in a household environment for safety, functionality, durability, and to ensure that it accomplishes the objectives of mitigating stovetop fires without a major disruption to consumers. Technology solutions must be proven effective and applicable to all types of cooking. Those that relate to the “Prevent Food Ignition in Pan-Contact Temperature Sensor” technology should meet the TFPG’s and their components should have a lifespan that match that of the current range.
It is noteworthy that the technologies that were identified as having the highest potential for success are consistent with some of the most effective strategies derived from the Fire Safety Concepts Tree analysis.
| Stovetop Mitigation Technologies | Fire Safety Concepts Tree Strategies | Sample Products |
|---|---|---|
| Detect and extinguish surface cooking fires | Manage stovetop fires by detection and extinguishment | Fixed extinguishing systems for residential stoves or kitchens |
| Prevent unattended cooking | Prevent stovetop fires by controlling interaction between element/fuel | Stove shutoff products based on motion sensor and/or timer |
| Prevent food ignition in pan | Prevent stovetop fires by controlling the element’s heat output | Thermostatically controlled heating elements |
Although these could be practical solutions for reducing cooking fires, the real challenge is incorporating these technologies into all homes. These products could be incorporated into the appliance either at the manufacturing stage or as an aftermarket retrofit product. Consideration must also be given to the additional monetary costs and impact to consumer cooking activities associated with these products to gain market-wide acceptance.
Finally, the use of technology to prevent or mitigate cooking fires is well summarized by the following statements from the U.S. Fire Administration study, “Behavioral Mitigation of Cooking Fires”:
“Technology can be used to prevent ignition or to mitigate the effects if a fire should occur. For example, technological systems that limit a stove’s heat or shut off the cooking equipment before or when a fire occurs have some obvious advantages. While it is imperative that individuals adhere to safe cooking behaviours, technology may the best long-term solution to dealing with the cooking fire problem. However, any technology solution must be proven effective and applicable to all types of cooking. In addition, to gain wide market acceptance, it must be inexpensive”. The study further concludes, “At this time, there are no implications for behavioural strategies on using technology to address the cooking fire problem”. 25
During the early 1990s, the National Research Council (NRC) initiated a comprehensive study to estimate the total economic cost of fire in Canada. They subsequently published the 1995 report, “Total Cost of Fire in Canada: An Initial Estimate”.17 The report estimated total fire related costs, which included direct losses attributed to injuries, deaths and property damage as well as indirect costs associated with maintaining the fire service, fire protection in structures, vehicles, equipment, insurance overhead, and other miscellaneous expenses. The results of this study estimated that the total annual cost of fire in this country is in the order of $11 billion (based on 1991 dollars), with the direct losses portion amounting to $2.9 billion (or 26%).
At the same time, the OFM commissioned a further study to establish the total cost of fire to Ontario using the same methodology developed for Canada. This was included as an appendix to the aforementioned main report.18 The total cost of fire in Ontario was estimated to be $4.2 billion (based in 1991 dollars), with the direct losses portion amounting to $940 million (or 22%).
In both studies, values of $2.4 million per death and $56,000 per injury were applied to fire casualties. These numbers were based on an analysis of cost factors relating to medical, funeral, pain/suffering, lost income and legal expenses. They are generally in line with statistical values established in similar cost of injury/death studies conducted by other jurisdictions.19,20,21,22
As previously mentioned, between 2003 and 2007, Ontario averaged 986 stovetop related fires that resulted in five deaths, 155 injuries and $17.6 million in property losses annually. Applying the NRC statistical values of life and injury estimates, actual reported property loss numbers, and Bank of Canada’s inflation rate calculator, the average annual direct cost attributed to stovetop fires is approximately $48 million in 2009 dollars.23
| Type of Fire Loss | 2003-2007 Average | Cost Estimate (1991 Dollars) | Cost Estimate (2009 Dollars)23 |
|---|---|---|---|
| Fatalities ($2.4 M/death) | 5 | $12 M | $17 M |
| Injuries ($56,000/injury) | 155 | $8.7 M | $12 M |
| Property Loss | $17.6 M | N/A | $19 M |
| TOTAL | $48 M | ||
It is noteworthy that this is a very conservative total, as it excludes the overhead type expenses that were captured in the NRC report. As these direct costs represent only 22% of the total cost of fire in Ontario, the $48 million estimate would be significantly increased if an appropriate portion of indirect costs were allocated to stovetop fires.
These strategies are generally consistent with stovetop cooking fire mitigation technologies that were identified as having the highest potential for success. Where situations cannot be addressed through technology, public education programs need to be developed.
a) Reduce the likelihood of unattended cooking.
For example, consideration should be given to modifying the following standards:
i) CAN/CSA-C22.2
No. 61-M89-Household Cooking Ranges
-4.21 Switches and Controls
Provide a timer feature that allows the user to manually preset cooking duration. At the end of the cooking cycle this feature should sound a continuous audible signal to alert the user and shut off the power to the element. The user must manually deactivate this audible signal and restore power if a longer cooking duration is necessary.
ii) ANSI Z21.1-2005-Household Cooking Gas Appliances
-1.2 General Construction and Assembly
Provide a timer feature that allows the user to manually preset cooking duration. At the end of the cooking cycle this feature should sound a continuous audible signal to alert the user and shut off the power to the element. The user must manually deactivate this audible signal and restore power if a longer cooking duration is necessary.
b) Reduce the likelihood of clothing ignition due to being placed in contact with the heating element.
For example, consideration should be given to modifying the following standards:
i) CAN/CSA-C22.2
No. 61-M89-Household Cooking Ranges
-4.14 Heating and Heater
Elements or 4.21 Switches and Controls
Limit the maximum surface element temperature to ensure that 100% cotton clothing material does not ignite within 5 seconds when placed in contact with the heating element.
Note: Demonstrations undertaken by the OFM with a smoothtop range resulted in 100% cotton material ignition at 8 seconds or longer at element temperatures near 530 C.30 Further analysis may be required to meet a 5 second criteria.
ii) CAN/CSA-C22.2 No. 61-M89-Household Cooking Ranges
-4.21 Switches and Controls
Revise 4.21.10 to increase the minimum height (currently 140 mm above element surface) of the backsplash element controls. Alternatively, relocate the controls to the front of the range with child resistant safety features incorporated into them.
iii) ANSI Z21.1-2005-Household Cooking Gas Appliances
-1.2 General Construction and Assembly
Revise 1.2.16 to increase the minimum height (currently 152 mm above element surface) of the knobs and buttons located on the backguard. Alternatively, models designed with knobs and buttons located at the front or top surface of the range should incorporate child resistant safety features.
c) Improve the durability of appliances that have shown superior fire safety performance.
Research conducted in developing this report indicates that smoothtop ranges may provide enhanced fire safety benefits from the perspective of reducing the risk of clothing ignition.30 However, the durability of the “Ceran” top in certain environments has been identified as a concern. Improvements in the smoothtop’s cooking surface durability will enhance marketability.
For example, consideration should be given to modifying the following standard:
i) CAN/CSA-C22.2
No. 61-M89-Household Cooking Ranges
-6.9.2 Investigation of
Glass-Ceramic Cook Top-Physical Abuse
Increase the steel ball mass and/or drop height used in test to improve the cooking surface’s durability.
d) Raise pubic awareness on the hazards of cooking fires.
For example, consideration should be given to modifying the following standards:
i) CAN/CSA-C22.2
No. 61-M89-Household Cooking Ranges
-5.1 Marking
Provide visible labels/markings on the front of the stove cautioning consumers on the hazards of unattended cooking, tipovers and placing combustible materials too close to the heating surface.
ii) CAN/CSA-C22.2
No. 61-M89-Household Cooking Ranges
-5.17 Marking
Provide a statement in the operating instructions, cautioning consumers on the hazards of unattended cooking, tipovers and placing combustible materials too close to the heating surface.
iii) ANSI Z21.1-2005-Household Cooking Gas Appliances
-1.28 Instructions
Provide a statement in the operating instructions cautioning consumers on the hazards of unattended cooking, tipovers and placing combustible materials too close to the heating surface.
iv) ANSI Z21.1-2005-Household Cooking Gas Appliances
-1.29 Marking
Provide visible labels/markings on the front of the stove cautioning consumers on the hazards of unattended cooking, tipovers and placing combustible materials too close to the heating surface.
Any technological solutions used to meet these performance goals should not severely impact cooking performance or introduce other safety issues. Where technologies designed to sense an over temperature condition are involved, the guidance provided in the Technical Feasibility Performance Goals (TFPG) developed by UL and CSA should be considered.29
1. According to the Ontario Fire Loss reporting system “cooking equipment” includes stove, range-top burner, oven, microwave, open fire barbeque (fixed or portable), range hood, deep fat fryer, other cooking items (e.g. toaster, kettle, electric frying pan, etc.)
2. Ontario Office of the Fire Marshal Fire Loss Reporting System
3. Council of Canadian Fire Marshals and Fire Commissioners, Fire Losses in Canada Annual Report (1998-2002).
4. Wijayasinghe, Mahendra S.; Makey, Thomas B., Fire Technology (May/June 1997-Volume 33), Cooking Oil: A Home Fire Hazard in Alberta, Canada.
5. Hall, John R. Jr., National Fire Protection Association, Home Fires Involving Cooking Equipment-February 2008
6. Smith, Linda; Monticone, Ron; Gillum, Brenda, Range Fires, U.S. Consumer Product Safety Commission, Hazard Analysis Division, Bethesda, MD, 1999, p 23 and 24.
7. Office of the Deputy Prime Minister, Fire Statistics, United Kingdom, 2004
8. New Zealand Fire Service, Emergency Incident Statistics-1 July 2004-30June 2005.
9. Duncanson, Mavis, New Zealand Fire Service Commission Research Report Number 16-Cooking, Alcohol and Unintentional Fatal Fires in New Zealand Homes 1991-1997.
10. Canadian Appliance Manufacturers’ Association, 2008 Major Appliance Industry Trends and Forecast.
11. NFPA 325-Guide to Fire Hazard Properties of Flammable Liquids, Gases, and Volatile Solids (1994 Edition, Amended 2001).
12. NFPA Fire Protection Handbook (Eighteenth Edition)-1998, Table 4-5C, p. 4-49
13. Hilado, Carlos J., Flammability Handbook for Plastics (Fifth Edition), 1998
14. Cafe, Tony, Fire Point-Physical Constants for Investigators, http://www.tcforensic.com.au/docs/article10.html
15. NFPA 550-Guide to the Fire Safety Concepts Tree (2002 Edition)
16. Little, Arthur D., Technical, Practical, and Manufacturing Feasibility of Technologies to Address Surface Cooking Fires, 2001.
17. National Research Council of Canada-Institute for Research in Construction, Total Cost of Fire in Canada: An Initial Estimate, 1995
18. Tridata, Total Cost of Fire in Canada: An Initial Estimate, 1995-Appendix A-Total Cost of Fire to Ontario
19. Rice, Dorothy P., MacKenzie, Ellen J., Cost of Injury in the United States-A Report to Congress-1989
20. Canada Gazette (Vol. 139, No. 5)-Regulations Amending the Motor Vehicle Safety Regulations (Locking and Immobilization Systems), 2005
21. Livernois, John, Value of Life Estimates in an Economic Cost Assessment, 2002
22. Hall, John R., National Fire Protection Association, The Total Cost of Fire in the United States, 2006
23. Bank of Canada Inflation Calculator, http://www.bankofcanada.ca/en/rates/inflation_calc.html
24. National Association of State Fire Marshals, Cooking Fires Task Force, Association of Home Appliance Manufacturers, Safe Cooking Campaign, Ten-Community Study of the Behaviors and Profiles of People Involved in Residential Cooking Fires-Executive Summary, July 1996
25. U.S. Fire Administration, Federal Emergency Management Agency, “Behavioral Mitigation of Cooking Fires”, August 2007, p. 54
26. CAN/CSA-C22.2 No. 61-M89-Household Cooking Ranges
27. ANSI Z21.1-2005-Household Cooking Gas Appliances
28. Office of the Fire Marshal, “Demonstration: Effect of Stovetop Element Temperature on Clothing Ignition”, 2008
29. Technical Feasibility Performance Goals, ANSI/UL Standards Technical Panel No. 858 Document Number: 858-04-01, 2004
30. Office of the Fire Marshal, “Electric Smoothtop vs. Coil Range Ignition Demonstration”, 2007
31. Age Distribution of Sample Electric Ranges in Recycling-Sample of 88 Electric Ranges in Recycling Facilities in 1997-excerpt from CAMA/AHAM presentation to OFM on June 23, 2008
32. Natural Resources Canada-Average lifetime expectancy of major
electrical appliances (in years)
http://oee.nrcan.gc.ca/residential/personal/appliances/lifetime.cfm?attr=4
The Fire Safety Concept Tree uses boxes and logic gates to define hierarchical relationships between multiple objective levels. Two types of logic gates namely, “or” gates and “and” gates are used for linking these levels. An “or” gate is represented by a circle with a plus sign in it while an “and” gate is represented by a circle with a dot in the middle. The “or” gate indicates that achieving any one of the sub-goal(s) will accomplish the outcome. The “and” gate indicates that achieving all of the sub-goals is necessary to accomplish the outcome.
In an example of an “or” gate, objective A is achieved if any one of sub-objectives B1, B2 or B3 can be achieved.
Figure B1: Example of an “or” gate
In an example of an “and” gate, objective A is achieved if all of objectives B1, B2 and B3 are achieved.
Figure B2: Example of an “and” gate
The following diagram represents the top gates of the Fire Safety Concepts Tree as provided in NFPA 550.
Figure B3: Fire Safety Concepts Tree
The tree’s top box is labeled “Fire Safety Objectives” and represents the ultimate goal that needs to be achieved. According to the tree’s logic, this task can be accomplished by either:
To prevent a fire from igniting, one of the following must occur:
To manage the impact of a fire one of the following must occur:
The following is a reproduction of the Fire Safety Concepts Tree as provided in NFPA 550 with some minor wording revisions to reflect the overall goal of mitigating stovetop fires.
Figure B4: Top Gates of Fire Safety Concepts Tree
The top box of the Fire Safety Concepts Tree represents the overall objective, which is to “mitigate stovetop fire”. To achieve this, the sub-objectives of “Prevent stovetop fire” and “Manage fire impact” are identified and connected to the overall objective through an “or” gate. This represents the concept that stovetop fires can be mitigated through either preventing the fire or managing the fire’s impact if one were to occur. Although only one of the two is required to achieve this, in reality satisfying both principles increases the likelihood of achieving this overall objective.
The “Prevent Stovetop Fire” branch of the tree is subdivided into three other categories through an “or” gate. Carrying out the strategies of controlling the heat from the element, controlling the interaction between the element and fuel (i.e. cooking oil, food, nearby combustibles, etc.) or controlling the fuel is sufficient to prevent a stovetop fire.
Figure B5: Prevent Stovetop Fire Branch of Fire Safety Concepts Tree
The heat emitted from a cooking element can be controlled by either limiting its energy output or limiting the cooking duration such that food items cannot be raised to its ignition temperature. This can be achieved manually by the homeowner, automatically by technology built into the appliance, or a combination of both.
Raising public awareness on the hazards of unattended cooking or encouraging homeowners to cook at lower temperatures through public education is effective to a degree. However, its dependence on appropriate human behaviour makes this an unreliable solution. Implementing stovetop technologies that automatically limit cooking temperatures or reduce the likelihood of unattended cooking are potentially effective solutions.
This component is connected to “Control heat transport”, “Control heat transfer process”, and “Control fuel transport” through an “and” gate. This means that the element should not be allowed to move too close to combustible materials, excessive heat should be prevented from being transferred to combustible materials, and combustible materials should not be allowed to move too close to the element. These inputs must all co-exist simultaneously in order to control the interaction between the element and combustibles.
With cooking operations, although one can limit the heat transfer process to a degree as discussed earlier, the fuel and heat source must remain in close proximity to each other at sufficient energy and duration due to the static nature of cooking activities. Hence, all three conditions cannot be simultaneously satisfied and the “Control element-fuel interaction” approach is not a practical solution when it comes to preventing oil/food ignition.
Where the control heat-fuel interaction component may be applied is in situations that involve the ignition of combustible non-food items that come into contact with the elements. This includes common accidental scenarios such as a person’s loose bathrobe sleeve, tea towels, or oven mitts brushing across a heated element. The “Control heat transport” sub-component is addressed by the fact that the element is stationary and cannot move towards combustible materials. The “Control fuel transport” and “Control heat transfer” sub-components can be simultaneously satisfied by ensuring combustible non-food items are not placed in close proximity to the elements. This action is highly dependent on appropriate human behaviour and is best addressed by raising homeowner awareness through improved public education programs.
The fuel can be controlled through elimination or by controlling its ignitability.
Eliminating the fuel means removing all combustible food and non-food items from around the heating element. Although eliminating food over a stovetop appears to be an impractical solution, one can still achieve this by considering alternative and safer cooking practices. For example, baking french fries in the oven instead of deep frying over the stovetop is a means of eliminating the fuel.
The ignitability of non-food items can be controlled by using those that are constructed of non-combustible materials. For example, using metal rather than wooden or plastic utensils is a means of achieving this. Newer TeflonTM based oven mitts are less ignitable than cloth oven mitts. These themes can best be conveyed through improved public education programs.
In the event of a fire, the “Manage Fire Impact” branch achieves the overall goal of mitigating the spread or size of stovetop fires. This component is subdivided into two categories, “Manage fire” and “Manage exposed” through an “or” gate.
Figure B6: Top Branches of Manage Fire Impact
The objective of managing a fire is to reduce hazards associated with fire growth and flame/smoke spread. According to the Safety Concept Tree, this can be accomplished by controlling the combustion process, suppressing the fire at its early stages, or controlling the fire by construction.
Figure B7: Manage Fire Branch of Fire Safety Concepts Tree
Controlling the combustion process involves controlling the rate of smoke and heat production by altering the fuel or the environment. As discussed earlier, the ignition properties of various food items are inherent to it and cannot realistically be altered. Changing the chemical composition of the kitchen environment, such as reducing normal oxygen levels is not a feasible solution either as this is habitable space. Hence controlling the combustion process is not an effective solution for managing stovetop fires.
Extinguishing a stovetop fire in its early stages is an effective means of managing fire impact. Fire suppression can be performed either automatically or manually. Automatic extinguishing systems that quickly detects and suppresses cooking fires is proven technology that is commonly used in commercial establishments as well as military housing. Transferring this technology to the home is a potentially effective solution for mitigating stovetop fires.
For manual fire suppression to be effective, a number of simultaneous events must occur in a timely manner including detecting the fire, deciding action, communicating the signal to the fire department, response time and suppressing the fire. In all cases, it takes significantly more time to manually suppress a fire than an automatic suppression system, making this a riskier, less reliable and less effective solution.
The third option for controlling stovetop fires is by constructing barriers or ventilation systems to physically contain the fire within a defined area or vent the fire to a safe location. As kitchen cabinets are often the secondary objects ignited, an effective strategy may involve protecting these and other areas vulnerable to secondary ignition. Controlling a fire by construction is an effective means for buying more time to take appropriate action, but it does not address the extinguishment of the fire.
The “Manage Exposed” branch is achieved by limiting the number of individuals and amount of property that are exposed to a stovetop fire. Alternatively, safeguarding these exposures will also achieve this goal. As the focus of this paper is on residential properties, there are limitations on how much personal property can be practically safeguarded in a home. Protection of vulnerable occupants within the home will need to be considered on a case by case basis. In general, the “Manage Exposed” branch is more applicable to an institutional building with vulnerable occupants rather than a home.
Applying the limitations within a stovetop fire situation to the Fire Safety Concepts Tree results in the following:
Figure B8: Fire Safety Concepts Tree for Mitigating Stovetop Fires
Hence the most appropriate strategies for mitigating stovetop fires include:
The Office of the Fire Marshal (OFM) has developed a number of public education resources and materials to increase public awareness of cooking-related fire hazards, safe cooking practices and fire safety.
These resources include the Put a Lid on It! educational program and a variety of television, radio and print public service announcements the fire service can distribute to local media. More information about these resources can be found by visiting:
www.makeitstop.ca
, or by calling the OFM at 416-325-3100
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