IMBSIR 75-788

Evaluation of the Fire Hazard

in a Mobile Home Resulting

from an Ignition on the Kitchen

Range

Edward K. Budnick and David P. Klein

Center for Fire Research

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

February 1 976

Interim Report

Prepared for Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D. C. 20410

NBSIR 75-788

EVALUATION OF THE FIRE HAZARD

IN A MOBILE HOME RESULTING

FROM AN IGNITION ON THE KITCHEN

RANGE

Edward K. Budnick and David P. Klein

Center for Fire Research

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

February 1 976

Interim Report

Prepared for Office of Policy Development and Research

Department of Housing and Urban Development

Washington, D. C. 20410

U.S. DEPARTMENT OF COMMERCE, Elliot L. Richardson, Secretary

James A. Baker, III, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

EVALUATION OF THE FIRE HAZARD IN A MOBILE HOME

RESULTING FROM AN IGNITION ON THE KITCHEN RANGE

Edward K. Budnick and David P. Klein

Abstract

A series of fire tests was conducted in a mobile home of

typical construction. The purpose of these tests, which were

completed in March 1975, was to evaluate the potential fire hazard

resulting from an accidental ignition from cooking on the kitchen

range. Specific attention was directed to (a) the ease of ignition

of the overhead kitchen cabinets as a function of the clearance

between the range and the underside of the cabinets with and without the presence of a metal hood, and (b) the flame spread following

the ignition.

The tests, in which a preheated pan of cooking oil was used as an ignition source, were conducted in a mobile home kitchen area.

The materials tested were printed lauan plywood, printed particle

board, and molded polystyrene, which are representative of materials

used in kitchen cabinet construction in mobile homes.

Under the test conditions employed, it was found that while the

time to ignition of the cabinet materials was only slightly affected

by the clearance between the cabinet bottom and the range, a significant time delay or no ignition resulted from the installation of a metal range hood.

An additional problem area revealed by the tests was the ignition and burn-through of the wall partition directly behind the

range.

Specific design recommendations based on test results are presented along with suggestions for further investigation.

Key words: Fire test; flame spread; kitchen cabinets; kitchen range;

kitchen range hood; limited combustibility; mobile home.

1. INTRODUCTION

This series of fire tests was conducted as part of a comprehensive

mobile home fire safety project with the overall objective being to obtain

experimental data on the potential growth and spread of fire in mobile homes

as affected by factors which include interior finish, room layout, and location of ignition. All of these considerations play an important role in the

kitchen area where the cooking range, as well as other energy consuming kitchen appliances, provide potential sources of ignition. It has been estimated

that 25 percent of mobile home fires originate in the kithcen [1]^.

The objective of this test series was to evaluate the possible fire

hazard due to the proximity to the cooking range of a number of types of

overhead kitchen cabinets. The testing was divided into 3 phases, each of

which was conducted in the kitchen area of an actual 12 x 65 foot (30.5 x 19.8 meter) mobile home. The floor plan is shown in figure 1.

Numbers in brackets refer to the literature references listed at the end

of this paper.

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Phase 1 consisted of 13 experiments designed to examine the type of potential fire sources and incident heat flux resulting from cooking on a kitchen

range

.

Phase 2 consisted of 12 tests where specific emphasis was placed on

evaluating the resistance of the underside of the cabinet directly above the

range as a function of the clearance provided. The ANSI Standard for Mobile

Homes, ANSI A119.1, 1974 edition, requirement for clearance above the kitchen

range is 30 inches (76.2 cm), unless (a) the cabinet above the cooking top is

protected with asbestos millboard at least 1/4 inch (0.64 cm) thick and covered

with sheet metal of minimum No. 28 manufacturer's standard gage, or (b) a metal venting hood of No. 28 standard gage is installed with 1/4 inch (0.64 cm)

air space between the hood and the cabinet bottom. If either of these design

features is included, a 24-inch (61.0-cm) minimum clearance is permitted.

Phase 3 consisted of 16 tests from which an evaluation was made of the

performance under fire conditions of the entire cabinet assembly directly

above the range, along with the cabinet assemblies adjacent on the left and

right, the ceiling above these 3 assemblies, and the wall directly behind the

range. The performance under exposure to the test fires i^as evaluated as a function of the material of the cabinet doors, the presence of a metal kitchen

range hood, the installation of a thin sheet of asbestos millboard on the

underside of the cabinet directly above the range, and the type of wall paneling behind the range.

In this study, no tests were conducted to evaluate the effects of (a) the

type of energy source utilized by the range (gas vs electric vs oil) , (b) the

time required for preheating, (c) malfunctions of the range, or (d) temperature,

humidity or other environmental conditions, since the ignition of the cooking

oil was the dominating factor.

When the effects of a range hood were investigated, a No. 26 manufacturer's

standard gage (corresponding to 0.017 in and 0.043 cm) steel overhead range

hood which was of the non-exhausting type and designed to provide a 5-inch

eyebrow (5-inch overhang) beyond the vertical surface of the cabinet face was

used (see fig. 2). This type of hood is typically used for collecting vapors

from cooking oil and grease over kitchen ranges in mobile homes. The installation of 1/4-in (0.635-cm) thick asbestos millboard on the underside of the

cabinet, recommended in ANSI 119.1, 1974 edition, paragraph 6.3.4.1, was

included among the 16 tests of Phase 3 to evaluate its effect on performance

of the cabinet system.

In Phase 2, temperatures were monitored in 12 locations on the surfaces

of the cabinets and wall above the range (see fig. 3). In Phase 3, the number

of locations was increased to 25. They were again located on the surfaces of

the cabinets and wall above the range and monitored not only temperatures at

surfaces near the ignition source but also on the ceiling above the range, on

the refrigerator in the kitchen, and on the far left wall of the kitchen (see

fig. 4). In addition, air temperatures were measured in several locations

inside the center cabinet itself and inside adjacent cabinets. In all cases,

temperatures were monitored using glass fiber insulated 24-gage, Chromel and

Alumel thermocouples. In Phase 2, the thermocouples were connected to a multiple point strip chart recorder. In Phase 3, the thermocouples were

connected to a high speed multiple channel data acquisition system.

3
4
2"x2" WALL STUD

KITCHEN WALL FACING

TOP VIEW

TEST SAMPLE

THERMOCOUPLE LOCATIONS

1 - Surface of Back Wall

2 - Submerged in Oil

3 - Directly Above Flame from Oil

4 - Exterior Surface of Right Cabinet

5 - Exterior Surface of Left Cabinet

6 - Interior Airspace of Left Cabinet

7 - Underside Surface of Left Cabinet

8 - Underside Surface of Right Cabinet

9-12 - Surface of Sample — Exposed & Unexposed Sides

Figure 3. Test Set-Up for Phase 2: Apparatus and Instrumentation Locations

5
Figure 4. Test Set-Up for Phase 3:

Apparatus and Instrumentation

Locations

6
2. EXPERIMENTAL DESIGN

2.1. Materials and Apparatus

A pan containing preheated cooking oil was ignited by a match after the

temperature of the oil reached approximately 38 0 °C. The oil then served as the ignition source, providing a fairly reproducible type of open flaming

ignition commonly resulting from kitchen activities.

The materials selected as representative of kitchen cabinet construction

were (a) 5/32-inch printed lauan plywood v/ith an ASTM E-84 tunnel test flame

spread rating corresponding to Class C (76-200) [2] and, (b) 1/2-inch printed

particle board. Cabinet doors installed in the test units were printed lauan

plywood and printed particle board of similar thickness to those above, and

hollow core molded polystyrene. All materials tested were selected from

actual mobile homes or were obtained directly from mobile home and kitchen

cabinet manufacturing plants.

For Phases 1 and 2, the section of cabinet directly over the range was

removed without alteration of the overhead cabinets adjacent to it in order to

provide space for a welded steel framework which v/as installed on top of the

gas-fueled kitchen range (see fig. 3). The frame was designed to hold cabinet

material samples above the range at heights varying between 9 and 33 inches

(22 . 9 and 83 . 8 cm)

.

For Phase 3, the framework was removed and cabinets were re-installed

above the range as in the original construction (see fig. 4). The system of

cabinets consisted of a center cabinet directly above the kitchen range, and

cabinets on the left and right adjacent to the center cabinet. There were

other cabinets in the kitchen area but only the three described above were

considered in the test procedure. Specifications for the three test cabinets

are as follows:

Left Adjacent Cabinet : Dimensions vzere 13.5 in wide x 28 in high x 12 in deep

(34.3 cm X 71.7 cm x 30.5 cm). The entire unit, including the door, was constructed of 5/32-inch printed lauan plywood stapled to 3/4 in x 1-1/4 in

(1.9 cm X 3.2 cm) pine framing. The door had a hollow core.

Right Adjacent Cabinet : Dimensions were 18.5 in wide x 28 in high x 12 in deep

(47.0 cm X 71.1 cm x 30.5 cm). The cabinet door also had a hollow core. This

cabinet was constructed in the same manner and using the same material as the

left adjacent cabinet.

Center Cabinet : Different cabinet units were installed directly above the

range to accommodate the different types of doors tested. However, the overall

enclosure dimensions were always 30 in wide x 24 in high x 12 in deep (76.2 cm

X 70.0 cm X 30.5 cm), and there were always 2 doors. Exact specifications for

these \inits are given in the appendix.

During the process of renovating the mobile home between Phases 2 and 3,

the refrigerator was removed, as well as the floor cabinet between the kitchen

range and the refrigerator. They were replaced by simulated units constructed

of 5/8-inch Type-X gypsum board on a frame of 2-inch x 2-inch pine. The dimensions of the cabinet (constructed of 5/8-inch gypsum) were 21 in wide x 37 in

high by 26 in deep (53.3 cm x 94.0 cm x 66.0 cm). The dimensions of the refrigerator were 29 in wide x 60 in high x 26 in deep (73.7 cm x 152.4 cm x 66.0 cm).

In addition, a piece of manufacturers standard 26-gage metal was placed on the

refrigerator side to closely simulate the thermal characteristics of an actual

refrigerator

.

7
2.2. Experimental Details — Phase 1

Phase 1 of the test series was conducted to determine the type of ignition

that would be used in testing the cabinets under a fire condition.

The equipment included an asbestos sample 24.5 in x 27 in (62.2 cm x 68.9

cm) with 4 holes provided for installation of heat flux transducers to measure

radiant and convective heat directly above the range burners (see fig. 5).

Initially, two calibrated, commercial heat flux transducers of the watercooled Garden type, were located in various combinations in the four holes in

the asbestos sample. These were used to determine the total heat flux incident

on the bottom surface of the kitchen cabinet directly above the range resulting

from the maximum output of any combination of two burners.

After determining the combination of two burners which provided the

maximum output of the range, the total incident heat flux was recorded as a function of distance above these two burners. This was accomplished by adjusting the height of the asbestos sample above the range from a minimum of 9 inches

(22.9 cm) to a maximum of 33 inches (83.3 cm).

The procedure was then repeated utilizing preheated 100% vegetable oil

in a 9-in (22.9-cm) diameter cast iron cooking pan. The pan was filled to a depth of 0.5 in (1.27 cm) which provided a surface area of 63.6 in^ (410 cm^),

and a volume of 31.8 in^ (521 cm^ ) for ignition of the oil.

In the test involving the preheated pan of vegetable oil, the range of

distances was limited from 21 in to 30 in (53.3 cm - 76.2 cm), a more practical

range when considering overhead cabinet construction. Total incident heat

flux was then recorded as a function of distance above the burning oil by a heat flux transducer placed directly above the center of the burning pan as was done when measuring the heat flux from the kitchen range burners.

2.3. Experimental Details — Phase 2.

Utilizing the open flame ignition source (preheated vegetable oil, in a 9-in diameter pan) pretested in Phase 1, a series of 12 tests were conducted

to evaluate the performance of a typical cabinet material at varying heights

from 22.5 in to 31 in (57.2 cm to 78.7 cm) above the ignition source on the

range

.

The 5/32-inch lauan plywood samples were precut to measure 27 in x 13 in

(68.9 cm X 33.0 cm) and fit into the frame assembly. Natural ventilation was

provided by partially opening windows in the test unit, but actual air movement was slight, and therefore disregarded. When the range hood was included,

it was placed in the apparatus and the sample was attached to the top side of

the hood.

In each test, cabinet doors were installed on the adjacent cabinets.

Both printed particle board and molded polystyrene cabinet doors were tested.

Temperature was monitored as a function of time at 12 locations, including

the exposed and unexposed sides of the sample, the adjacent cabinet surfaces

and walls, and cabinet door (fig. 3). The temperatures were recorded on a 24-

point chart recorder. Observations were made and recorded for changes in

sample performance and progress of the fire.

The duration of the fire was limited in order to prevent excessive damage

to the apparatus and the kitchen area. The fire was extinguished when it

appeared to the test observers that extensive involvement would result from

continuation.

8
2.4. Experimental Details — Phase 3 Utilizing the open flame ignition source (preheated vegetable oil) , a series of 16 tests was conducted to evaluate the performance of the system of

3 cabinet assemblies located above the range using doors constructed of a variety of materials on the center cabinet (see fig. 4). The range hood, when

used, was screwed onto the underside of the center cabinet. In addition, a 12 in X 30 in X 1/4 in (30.5 cm x 76.2 cm x 0.64 cm) piece of asbestos millboard was installed between the hood and the underside of the center cabinet

in six of the tests. Hollow core lauan plywood doors of identical construction

to those described in section 2.2, were used on the adjacent cabinets for all

16 tests.

A 10-inch (25,4-cm) diameter pan was substituted for the 9-inch pan for

Phase 3. It was filled to 0.5 in (1.27 cm) which provided a surface area of

78.5 in^ (506. 5 cm^) and a volume of 39.25 in^ (643 cm^ for ignition of the

preheated 100% vegetable oil. In one case (Test 12), the depth of the vegetable

oil was reduced to 0.25 in (0.64 cm).

Temperature was monitored as a function of time at 25 locations, fed

through a high speed multi-channel data acquisition system and recorded on a magnetic tape, which was then processed by computer. Thermocouple locations

included the air space inside of the center cabinet; the air space inside and

surface of both adjacent cabinets; and the surface of the back wall, the

ceiling, the far left wall, and the refrigerator (see fig. 4). Observations

were recorded concerning the performance of the cabinet material and the

progress of the fire. The construction of the exposed back wall behind the

range was varied among the tests to include (a) 5/32-inch lauan plywood

(typical), (b) 5/8-inch Type-X gypsum board, and (c) 5/32-inch lauan plywood

over gypsum board.

9
f The duration of the fire was limited, as in Phase 2, to prevent complete

destruction of the kitchen area so that subsequent tests could be conducted

without extensive rebuilding.

3. TEST RESULTS

3.1. Data from Phase 1 — Incident Heat Flux Measurements

At a constant height of 9 inches (22.9 cm) above the range top, the maximum incident heat flux from the range was determined to be 0.84 + 0.02 Btu/ft^

s (0.96 + .02 W/cm^). This was obtained when the back left gas burner was

adjusted to maximum output. The variation was a result of some contribution

from one of the other burners, since this part of the test was conducted

utilizing combinations of two burners at one time.

The combination which provided the maximum total incident heat flux of

0.8 Btu/ft^ s (0.96 W/cm^) was the two back burners in a state of maximum output

When this source was held constant and the height of the sample was varied,

the total incident heat flux ranged from 0.85 Btu/ft^ s (0.97 W/cm^) at 9 inches

(22.9 cm) to 0.11 Btu/ft^ s (0.12 W/cm^ ) at 30 inches (76.2 cm). Figure 6 shows

these results.

Figure 7 shows the results of the second part of Phase 1, when the pan

of vegetable oil was utilized. The total incident heat flux ranged from 3.18

Btu/ft^ s (3.61 W/cm^) at a distance of 21 inches (53.34 cm) above the flame

source to 1.5 Btu/ft^ s (1.72 W/cm^) at 30 inches (76.2 cm). From this it

was assumed that while two burners alone may not provide sufficient heat to

readily ignite the material samples, there would be sufficient total incident

heat flux output from a kitchen fire incident involving cooking oil to ignite

materials utilized in the immediate area of the range, specifically cabinets.

It was also determined that a cooking oil fire over either back burner caused

a greater buildup of heat than a fire over either front burner since the rear

burners are more enclosed (by the back wall partition and overhead cabinets)

than the front burners. Using this information, Phase 2 of the test series

was initiated.

3.2. Data from Phase 2 — Cabinet Material Tests

Table 1 illustrates the recorded test data collected for each test; the

data is grouped into 3 areas for simplification:

1) the test conditions,

2) key points in the progression of each test as a function of time, and

3) maximijm temperatures reached at critical locations.

3.3. Data from Phase 3 — Cabinet Assembly Tests

Table 2 illustrates the recorded test data collected for each test.

Again, the data is organized into 3 groups as above.

4. DISCUSSION

4.1. Phase 2 — Cabinet Material Tests

The series of tests conducted in Phase 2 provide experimental data supporting an initial assumption that the distance above the burning oil directly

affects the time at which ignition of combustible cabinet material occurs.

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of Burning Vegetable Oil Placed on a Kitchen Range

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Further, the tests indicate that a cooking oil fire of the type used for this

test series may result in ignition of the surrounding combustible cabinets or rear wall in as little as 1 minute-15 seconds (Test 6).

In analyzing the results of Phase 2, the data from Test 8 was not included

since that test fire did not develop to a level comparable with the other 11

tests

.

Under the conditions where either rear burner was used and a hood was not

installed above the range, all of the samples ignited. The shortest time

(1 minute-15 seconds) to sustained burning of a sample occurred at a distance

of 22.5 in (57.15 cm). The longest time (3 minutes-10 seconds) occurred at a sample height of 30 in (76.2 cm). The total time range was 1 minute-55 seconds.

Both of these represent extremes in construction practicality, but even at a more typical height of 25 in (63.5 cm) , sustained ignition occurred at 2 minutes10 seconds (Test 7 )

.

In the series of tests where a manufacturers standard No. 26 gage steel

hood was installed, the performance of the material samples was notably different. For example, in Test 5 , at a distance of 22.5 in (5'7.15 cm) sustained

ignition did not occur until 4 minutes-45 seconds, which is greater by more

than a factor of 2, than the time associated with sustained ignition of the

sample at 30 in (76.2 cm) without the hood in Test 2. Furthermore, at heights

of 26 in (66.04 cm) and 31 in (78.74 cm), there was no ignition of the sample

above the hood, although ignition of the side cabinet and back wall occurred.

Test data indicate that there is a fire potential due to exposure of

adjacent cabinets. In a number of the tests where the height of the sample

material above the range was 25 in (63.5 cm) or greater and the hood was not

installed, a cabinet adjacent to the sample ignited within 30 seconds prior

to the sample (Tests 7, 9). In 2 out of 3 of the tests where the hood was

installed, an adjacent cabinet ignited while the overhead sample did not

(Tests 10, 11). It was also discovered that the installation of a hood

resulted in an increased problem with the back wall due to re-radiation and

exposure of the wall to high temperature turbulent convection occurring where

the hood and back wall meet.

It should be noted that these general conclusions are directed specifically at the performance of a Class C (ASTM E-84 Tunnel Test) lauan plywood

paneling which was found to be the typical construction material used for

cabinet undersides and wall construction in the three test units.

One test was conducted in Phase 2 (Test 12) where a sample of molded

polystyrene was placed at 26 in (66.04 cm) and a hood was installed. While

the results are limited, the sample deformed and ignited in 3 minutes while in

a similar test of Class C lauan plywood (Test 11) , there was no ignition of

the sample. This warranted further investigation in Phase 3 due to a potential trend in the materials industry to provide molded polystyrene cabinet

construction [3]

.

There was some difficulty in reproducing the ignition source. Preheating

times varied due to the buildup of residue in the pan which could not be

removed after every test. And, even though ambient conditions were not considered a test variable, it is suspected that ambient temperature and humidity

also may have slightly affected the time it took to reach ignition of the oil.

The excessively low temperatures produced in Test 8 were attributed to these

problems. As was mentioned previously. Test 8 was not included in the analysis.

Further, the testing was limited to the immediate area of the range.

Sufficient time was provided for both horizontal and lateral propagation of

the fire, but the severity was limited by the test group in order to provide a

15
reasonable level of reproducibility. It was anticipated by the test personnel

that continuation of any of the tests (excluding Test 8) would have resulted

in involvement of the entire kitchen area which would have destroyed the test

apparatus.

4.2. Phase 3 — Cabinet Assembly Tests

The series of 16 tests in Phase 3 was conducted to evaluate the performance of kitchen cabinet assemblies, including a variety of design modifications, under conditions resulting from the ignition of a pan of vegetable

oil.

In every test where the assembly did not include a metal range hood and

asbestos millboard insulation, the surface of the cabinet doors, regardless of

the door material, ignited within the range of 20 to 25 seconds after flame

impingement on the bottom surface of the cabinet (Tests 4, 7, 8, 11, 12). In

addition, the maximum ceiling temperatures produced were significantly higher

for those assemblies which did not include a metal range hood.

When a metal range hood was included in the assembly the time period from

when the ignition source first impinged on the exposed side of the assembly to

ignition of the cabinet assembly itself was increased significantly (see figs.

8 and 9). In most cases the time period was increased by a factor of 4 or 5.

(Comparison of tests 6 and 7 provide an illustration. In Test 7, the time

period in question was 20 seconds; in Test 6, with a similar cabinet assembly,

but with a metal hood installed, the time was increased to 2 min-25 s)

.

There was a significant decrease in the maximum temperature recorded on the exposed side of the cabinet bottom when, along with a hood, 1/4-inch

asbestos millboard was utilized as an insulator. Comparison of tests where

the asbestos millboard and range hood were installed against tests of similar

cabinet materials when neither the hood nor the millboard were used, show that

the installation of the asbestos millboard and the hood decrease temperatures

on the exposed side of the cabinet by at least a factor of 2 (Tests 4 and 16,

11 and 6, 8 and 13)

.

In Phase 2, it was recognized that the exposed wall behind the range in

the kitchen may pose a serious potential for flame propagation beyond the

immediate area of the range. Therefore, in Phase 3, the construction of the

back wall was altered to include 5/32-inch lauan plywood for some of the

tests, and 5/8-inch gypsum board for others (5/8-inch gypsum was used due to

availability; it is the authors' opinion that 5/16-inch gypsum board would

have been adequate)

.

In Tests 1, 5, 8 and 16, analysis of the test data supported the conclusion from Phase 2 that the installation of a metal range hood reduces the

time to sustained ignition of a back wall constructed from 5/32-inch lauan

plywood.

In Tests 1, 5, and 16, the use of 5/32-inch lauan plywood with an ASTM E84 flame spread rating of Class C (76-200) resulted in burn-through to the

adjacent bedroom (see fig. 10) exposing the electrical wiring in the wall

partition as well as providing the flames with a vertical path into the ceiling

cavity. The Class C material also allowed lateral propagation, including

flame impingement on the refrigerator. Observations from Test 16 indicate

that impingement on the refrigerator occurred at 1 min-35 s. This test was,

however, somewhat more dramatic than Tests 1 and 5, and it appears as though

the low relative humidity in Test 16 may have contributed to this. The time

recorded for Test 1 was 4 minutes, which was under more normal environmental

conditions.

16
Figure 8. Illustrates the Extent of Involvement of a Cabinet

Assembly Without a Metal Range Hood (Time: 2 min-20 s)
Figure 10. Illustrates Burn-Through

of the Back Wall in Test 16; the

Wall was Constructed of 5/32-inch

Printed Lauan Plyv/ood

18
In Test 8, the 5/32-inch lauan plywood was installed over a subsurface of

5/8-inch gypsum board. Test observers noted that while penetration (burnthrough) of the partition was prevented, the lateral propagation across the

back wall was only slightly impaired.

In the tests which utilized a 5/B-inch gypsum board partition, there was

no evidence of failure of the partition or lateral propagation beyond the area

of direct impingement of the ignition source. While these tests were not designed specifically to evaluate the fire

hazards associated with various types of cabinet door materials, the test data

and observations did provide some interesting information.

In analyzing the data from those tests in which the assembly did not

include a metal range hood or a 1/4-inch asbestos millboard insulator, the

most severe temperatures reached at the ceiling occurred when the cabinet

doors were constructed of molded polystyrene. However, in those tests which

included the hood, and/or the asbestos millboard, there were no appreciable

differences in temperatures associated with the type of material used for the

cabinet doors.

In all three tests in which polystryene doors were tested, the door

assemblies failed (see fig. 11), resulting in greater temperatures inside the

cabinet and ignition of the countertops and the vinyl flooring due to direct

exposure from the melting and burning cabinet door debris. However, as the

doors melted and dripped away from the cabinet assemblies, ceiling temperatures

were reduced. Greater quantities of smoke and irritants were noted by observers during the tests which included the molded polystyrene doors than during

the other tests.

Figure 11. Illustrates the Performance of a Molded

Polystyrene Cabinet Door (left) and a Printed Particle

Board Cabinet Door (right) to a Test Fire. In this

Test a Metal Range Hood was Installed.

19
In the tests in which lauan plywood and/or particle board doors were

tested, there was no failure of the door assemblies. While production of

irritants and smoke was less, and maximum temperatures in the cabinets were

lower, the ceiling temperatures were considerably greater than during the

tests with polystyrene doors. It appears that when the polystyrene doors

distorted and began to melt down, the temperatures at the ceiling were reduced

due to a reduction of fuel near the ceiling. In those tests where lauan

plywood or particle board doors were installed, ceiling temperatures continued

to increase.

The tests were conducted under full-scale conditions in an actual mobile

home. Therefore, environmental effects were controlled only to the point of

maintaining the interior temperature at approximately 20 °C (68 °F) . Relative

humidity varied somewhat throughout the test series and therefore would be

expected to have some minimal effect on the test data.

Finally, Test 15 was not included in the analysis due to failure of the

ignition source to develop fully. This failure was attributed to difficulties

in the preheating state of the test and, as with Test 8 of Phase 2, to environmental conditions (specifically high relative humidity)

.

J . - 5. SUMMARY

Based on the limited tests reported here, the following summary appears

justified:

1. A pan of cooking oil which burns freely for as little as 40

seconds on a range in a mobile home kitchen represents a risk

of fire and involvement of the cabinets and back wall in the

kitchen area.

2. For the range of clearances studied [22.5 to 31 in (57.2 to

78.7 cm)), the height to the bottom surface of the cabinet

directly above the range has a slight affect on the time it

takes to reach sustained burning of the cabinet. Without a metal range hood, sustained burning of the Class C cabinet

underside occurred within 3 minutes in the majority of tests

a cooking oil fire.

3. Installation of a range hood of a design similar to that used

in the test series provides significantly improved resistance

to sustained burning of the underside of the cabinet directly

above the range, significantly reduces the rate of temperature

rise and maximum temperatures at the ceiling above the range,

and increases the time to ignition of the vertical surfaces of

the cabinet assembly, including doors and trim.

4. Installation of 1/4-inch asbestos millboard between the underside of the cabinet and the metal range hood provides a significant reduction in temperatures transmitted to the cabinet

underside. However, due to direct exposure, this does not prevent ignition of the cabinet in all cases.

5. Cabinets adjacent to the cabinet directly above the kitchen

range can be ignited from a cooking oil fire, but not as readily

as the cabinet directly above.

20
6. The partition behind the kitchen range represents a critical

area for lateral flame spread and for fire penetration into the

adjacent room due to a cooking oil fire on a rear burner.

The presence of a range hood tends to increase this potential

for the typical Class C partition material.

7. Kith a range hood installed, the differences in performance of

the 3 types of cabinet door materials were less pronounced than

with a range hood not installed. However, in all of the tests

with polystyrene cabinet doors, there was a structural collapse

of the door.

6. RECOMMENDATIONS

Based on experimental test results, there are two principal design

recommendations which may be employed to minimize fire hazards associated

with kitchen range fires in mobile homes:

1. It is recommended that a sheet metal hood (minim^jm No. 2 6 manufacturer's standard gage) be provided above the range with a minimum clearance above the range top of 24 inches. This hood

should include a 5-inch eyebrow (overhang) to prevent direct

impingement of a flame on the front vertical surfaces of the

cabinet doors (see figure 2 for details of the range hood

design utilized in this test series) . In those cases where the

hood and overhead cabinet are recessed, the exposed sides of

adjacent cabinets should be protected by an extension of the

hood design. It is also recommended that a sheet of minimum

1/4-inch asbestos millboard (or equivalent) be provided between

the metal range hood, and the underside of the cabinet above

and the sides of the adjacent cabinets. The underside of the

adjacent overhead cabinets should be constructed of materials

having a maximum flame spread rating not greater than 5 0 when

tested in accordance with the Standard Method of Test for

Surface Burning Characteristics of Building Materials, ASTM E84-

70 [2], and a rating of limited combustibility as defined in

NFPA No. 220, Types of Building Construction, 1975 edition [4].

2. It is recommended that the material comprising the exposed partition behind the range be limited to a material having a flame

spread rating of not greater than 50 (under ASTM E-84) and a rating of limited combustibility (under NFPA 220, 1975 ed.) to

prevent fire penetration into adjoining areas. This material

should be attached by mechanical means and extend at least IB in

(45.7 cm) beyond the edge of the range to cover the area of

flame impingement.

The experimental test data indicate that the difference in performance of

the three types of cabinet doors (5/32-inch printed lauan plywood, 1/2-inch

printed particle board, and molded polystyrene) was not vitally significant in

that, while specific burning characteristics did differ somewhat between the

different types of doors, the overall fire severity was similar. However,

from observations it was noted that the production of smoke was significantly

higher in those tests utilizing molded polystyrene. Therefore, it is recommended that laboratory testing be conducted to provide data on smoke generation

for the materials tested.

21
7 . ACKNOWLEDGEMENTS

The tests reported here were conducted by the authors and the following

members of the Center for Fire Research: Mr. J. R. Lawson, Mr. T. F. Maher

and Mr. W. I. Stull. Their efforts are greatly appreciated.

The project was supported in part by funds provided by the Mobile Home

Manufacturers Association, Chantilly, Va.

Appreciation is expressed to the Kitchen Cabinet Manufacturers Association

for providing a number of the kitchen cabinet assemblies used in the testing.

8. REFERENCES

[1] Tyron, G. H. , A Talk on Mobile Homes and Fire Safety, presented to the

101st Annual Convention of the Firemen's Association of the State of New

York, MH/RB Document No. 73-8 (Sept. 1973).

[2] Standard Method of Test for Surface Burning Characteristics of Building

Materials, ASTM E84-70, American Society for Testing and Materials,

Philadelphia, Pennsylvania (1970).

[3] Hall, A., Plastics are Rolling into Low-Cost Housing via the Mobile

Home Route, Modern Plastics, Vol. 49, No. 6, 58-61 (June 1972).

[4] Types of Building Construction, NFPA 220-1975, National Fire Protection

Association, Boston, Massachusetts (1975).

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NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBSIR 75-788

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Evaluation of the Fire Hazard in a Mobile Home Resulting

from an Ignition on the Kitchen Range

5. Publication Date February 1976

6. Performing Organization Code

7. AUTHOR(S)

Edward K. Budnick and David P. Klein

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 4926389

11. Contract/Grant No.

12, Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Office of Policy Development and Research

Department of Housing and Urban Development

Washington. D.C. 20410

13. Type of Report & Period

Covered

Interim Report

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most si^ificant information. If document includes a significant

bibliography or literature survey, mention it here.)

A series of fire tests was conducted in a typical mobile home to evaluate the potential

fire hazard resulting from an accidental ignition from cooking on the kitchen range.

Specific attention was directed to (a) ease of ignition of the kitchen cabinets as a function of the clearance between the range and the underside of the cabinets with and

without the presence of a metal hood and (b) flame spread following the ignition.

The tests, which used a preheated pan of cooking oil as an ignition source, were con- ducted in a mobile home kitchen area. The materials tested were printed lauan pljnjood,

printed particle board, and molded polystyrene, representative of materials used in

kitchen cabinet construction in mobile homes.

Under the test conditions employed, it was found that ignition of the kitchen cabinets

occurred in all cases in which a metal hood was not used. The time to ignition of

the materials was only slightly affected by the clearance between the specimen (cabinet

bottom) and the range. A significant time delay or no ignition resulted from the

installation of a metal range hood.

An additional problem area revealed by the tests was the ignition and burn-through of

the partition directly behind the range.

Specific design recommendations based on test results are presented along with suggestI t»i ?-i I II r I I.I r I iitfi—I iivea l i ^ci l i i.ii i 17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons) ^..^^ ^^^^^ Spread; kitchen cabinets; kitchen range;

kitchen range hood; limited combustibility; mobile home.

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1

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USCOMM-DC 29042-P74