NBSIR 73-267

Report of Fire Tests on Flexible

Connectors in HYAC Systems

Lionel A. Issen

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

July 1973

Final Report

Prepared for American Iron & Steel Institute

New York, New York 10017

NBSIR 73-267

REPORT OF FIRE TESTS ON FLEXIBLE

CONNECTORS IN HVAC SYSTEMS

Lionel A. Issen

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

July 1973

Final Report

Prepared for American Iron & Steel Institute New York, New York 10017

U. S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director

REPORT OF FIRE TESTS

ON

FLEXIBLE CONNECTORS IN HVAC SYSTEMS

Abstract

The contemporary high rise building with its central air conditioning

system and high content of synthetic materials presents a potentially

higher fire and smoke hazard than those erected prior to 1950. The fire

penetration and the transportation of fire, hot gases, noxious fumes and

smoke through the duct system is an important factor affecting the designers' and building code concept of compartmentalization and life

safety of occupants. Since air ducts penetrate fire barriers, the duct

materials, the flexible connectors between the ducts, and the terminal

units are all important elements that can affect the actual fire endurance

of the fire barrier.

Flexible connectors made of four different materials (aluminum, galvanized

steel, glass fiber and woven glass fiber) and two attachment techniques

were subjected to fire tests which conformed to the Standard Method of

Fire Tests for Building Constructions and Materials, ASTM E 119. The

results show that in order to maintain the integrity of a fire barrier

penetrated by a duct or flexible connector, the duct and connector must

maintain their integrity for the period of the fire exposure, the connectors must remain tightly attached to the duct, and the penetrations through

the fire barrier must be suitably blocked (fire stopped) at the edge of

i
the opening. The tests also showed that rubber and plastic components

in the terminal units can produce significant amounts of irritating smoke

which can spread into the room and hence to other parts of the buildings.

Key Words: Aluminum; ductwork; fabric; fire tests; glass fiber; high

rise buildings; HVAC systems; steel; terminal units.

ii
TABLE OF CONTENTS

Page

ATjstract i

LIST OF ILLUSTRATIONS v

1.0 INTRODUCTION 1

2.0 PILOT TEST 3

2.1 Description of Test (NBS Test 512) 3

2.2 Furnace Closure 4

2.3 Flexible Connectors.... 4

2.4 Instrumentation 5

3.0 EVALUATION TEST 6

3.1 Description of Test (NBS Test 516) 6

3.2 Furnace Closure 8

3.3 Flexible Connectors 8

3.4 Instrumentation 10

3.4.1 Glass Fiber Connectors 11

3.4.2 Steel Connectors 10

4.0 TEST RESULTS 11

4.1 Pilot Test (NBS Test 512) 11

4.1.2 General Observations 11

4.2 Evaluation Test (NBS Test 516) 11

4.2.1 Temperature Observations 12

4.2.1.1 Furnace Temperatures 12

4.2.1.2 Connector Assembly Temperatures 12

4.2.1.3 Glass Fiber Connectors 12

4.2.1.4 Steel Connector Temperatures 14

iii
4.2.1.5 Comparison Data 14

5.0 DISCUSSION AND SUMMARY OF RESULTS 15

5.1 Temperature and Fire Endurance 15

5.2 Smoke and Toxic Gases 16

5.3 Comparison of Square and Round Ducts 17

5.4 Performance Considerations 18

6 . 0 ACKNOWLEDGEMENT 19

APPENDIX A: Observation During Pilot Test (NBS 512) 20

APPENDIX B: Observation During Evaluation Test (NBS 516) 22

BIBLIOGRAPHY 25

iv
LIST OF ILLUSTRATIONS

Figure

1 Test 512 Typical Layout Showing Flexible Connector Assembly

2 Test 512 View of Raised Furnace Closure

3 Test 512 View of Steel Connectors, Showing the Vinyl Covering

and Attachment to the Duct

4 Test 512 View of Aluminum Connector Showing Vinyl Cover and

Attachment to the Duct

5 Test 512 View of Steel Flexible Connectors at Terminal Unit

6 Test 512 View of Aluminum Flexible Connector at Terminal Unit

7 Test 512 Architectural Enclosures in Place

8 Test 512 Aluminum Flexible Connector (Note method of blocking

penetrations through closure.)

9 Test 512 Thermocouple Layout

10 Test 516 Top View of Furnace Showing Flexible Connector Test

Layout

11 Test 516 Construction and Thermocouple Details for Glass Fiber

Flexible Connectors

12 Test 516 Construction Details for Steel Flexible Connectors

13 Flange Plates

14 Penetration Through Closure

15 Typical Duct Showing Glass Fiber Blanket and Connector Function

Point

16 Test 516 Thermocouple Layout for Steel Flexible Connector and

ONYP Terminal Units

17 Test 516 Furnace Temperatures

18 Test 516 5 Inch Glass Fiber - Temperatures Along Connector

19 Test 516 5 Inch Glass Fiber Temperatures Along Terminal Unit

and Architectural Enclosure

V
Figure

20 Test 516 5 Inch Glass Fiber - Air Temperature Architectural

Enclosure

21 Test 516 5 Inch Woven Glass Fabric - Temperatures Along Corridor

22 ^" Test 516 5 Inch Woven Glass Fabric - Temperatures Along Terminal

Unit and Architectural Enclosure

23 Test 516 5 Inch Woven Glass Fabric - Air Temperatures

Architectural Enclosure

24 Test 516 5 Inch Galvanized Steel - Temperatures Along Connector

25 Test 516 5 Inch Galvanized Steel - Temperatures Along Terminal

n Unit and Architectural Enclosure

26 Test 516 5 Inch Galvanized Steel - Air Temperatures Architectural

Enclosure

27 Test 516 6 Inch Galvanized Steel - Temperatures Along Connector

28 6 Inch Galvanized Steel - Temperatures Along Terminal Unit and

Architectural Enclosure

29 Test 516 6 Inch Galvanized Steel - Air Temperature Architectural

Enclosure

30 Test 516 Comparison of Outlet Air Temperatures on Architectural

Enclosures

31 Separation of 5 Inch Steel Connectors from Main Duct

32 Smoke Emitted at Architectural Enclosures

33 Comparison of Charring Inside the ONYP Terminal Units for the

5 and 6 Inch Diameter Steel Assemblies

vi
REPORT OF FIRE TESTS

ON

FLEXIBLE CONNECTORS IN HVAC SYSTEMS

1.0 INTRODUCTION

Compared to the buildings prior to 1950, the modern high-rise building

with its central air conditioning system and high content of synthetic

materials presents a greater hazard to life and to property in the event

of fire. Current construction practices and code requirements must be

continuously revised to cope with these factors.

One of the factors affecting the fire integrity of the building relates

to the ability of the duct work to resist fire breaking into the duct

and being carried through a fire resistive floor barrier via the duct

system. An important component of the duct system is the flexible

connector between the duct and the terminal unit on a floor above. The

junction of the connector to the duct, the penetration of the connector

through the fire resistive floor, and the materials used in the connector

assembly can be sources of failure.

At the beginning of this program, a brief survey of the literature was

made, which uncovered only a small amount of research information relating

to the fire performance of flexible connectors and duct systems [1,2,3],

This report summarizes the results of two tests designed to indicate the

fire performance of flexible connectors as installed in a typical floorceiling construction.

1
A pilot test (NBS Test 512) was laid out to examine the qualitative

differences between the performance of flexible connectors of aluminum

and of galvanized steel, to test the effectiveness of maintaining the

integrity of the fire barrier, and to test a method of attaching the

flexible connectors to a main duct.

Based on the results of the pilot test, an evaluation test (NBS Test 516)

was laid out in which 2 non-metallic flexible connectors and 2 galvanized

steel connectors were evaluated for their relative effectiveness in

maintaining the fire barrier. Changes were made in the method of

attaching the flexible connectors to the main duct and in the method

of penetrating the fire barrier, compare the details on figures 1 and 12.

The second test was also used to examine an assembly similar to the one

used in the One New York Plaza building at the time of the fire in August

1970. [4] . , .

At the present time there are no established fire test failure criteria

for flexible connector assemblies. The criteria used to evaluate the

flexible connector assemblies in this study was based on the temperature

rise criterion for building construction assemblies in ASTM E 119. Thus,

a temperature rise of 139°C (250°F), at the outlet of the architectural

enclosure was taken as the termination point or effective fire endurance

time. This criterion ensures that combustible materials such as drapes,

papers, furnishings, that may be in contact with, or close to, the architectural enclosure will not be ignited for the period of the rating.

2
2.0 PILOT TEST

2.1 Description of Test (NBS Test 512)

In the pilot test a 24 inch x 24 inch square duct 10 ft in

length was hung from a ceiling closure constructed over the NBS

floor furnace. In order to clear the duct over the furnace

burners, it was necessary to build a hood-type closure

which extended about 24 inches above the top of the

furnace. See Figure 1 which shows the test layout and

Figure 2 which shows a side view of the closure.

Three round flexible connectors (4 inch dia. aluminum, 4 inch

dia. glavanized steel, and 6 inch dia. glavanized steel) were

attached to the duct on the inside of the furnace, and through

through the roof of the furnace to a simulated box type terminal

unit. Each simulated terminal unit was in turn covered with a

sheet metal architectural enclosure. The terminal units

were of a size comparable to those used to provide heating

and cooling capacity for an average size office or apartment

module; and the architectural enclosures were sized to provide

reasonable erection clearances around the terminal unit.

Figure 3 shows the two steel connectors attached to the

main duct; Figure 4 shows the aluminum connector attached

to the main duct; Figure 5 shows the steel connectors

attached to the terminal units; Figure 6 shows the aluminum

3
connector attached to the terminal unit; and Figure 7 shows

the architectural enclosures in place.

iThe ducts were designed and manufactured by a local contractor in accordance with current design standards. [5]

2 . 2 Furnace Closure ^

The furnace closure consisted of a 2 x 4 (nominal) studs, 16 inch

on center, forming the side walls and 2 x 10 (nominal) joists,

16 inch on center, forming the top. The inside of the closure

was covered with two sheets of 5/8 inch type X gypsum board,

which was protected with expanded metal lath and sprayed

vermiculite plaster in order to provide a barrier with a

minimum fire endurance of 2 hours.

The separations (gaps) between the flexible connectors and

the hole through the furnace closure were packed with glass

fiber, and were protected on the fire side with a steel flange

plate. The steel flange plate was supplied by the manufacturer

of the flexible connectors. Figure 8 shows the method of

blocking the penetrations through the furnace closure.

2 . 3 Flexible Connectors

The flexible connectors consisted of a 4 inch diameter

aluminum connector, a 4 inch diameter galvanized steel

connector and a 6 inch diameter galvanized steel
connector. This provided a comparison of two materials

and a comparison of two sizes of steel connectors.

The flexible connectors were attached with steel friction

strips to a standard flange plate attached to the duct; the

details can be seen in Figures 3 and 4.

The duct was covered with a rated 2-inch thick glass fiber

blanket. This was attached with a rated adhesive.

Inside the furnace the flexible connectors were covered

with one inch fiber glass and a vinyl dust cover. Outside

of the furnace enclosure the connectors were uncovered.

This is in accordance with field procedures where the

connector and duct may be insulated within a plenum or chase

formed by the ceiling and the floor slab above it.

Both the duct and the portion of the flexible connectors

that were inside the furnace were painted with a rated

vapor barrier.

2.4 Instrumentation

The main duct was instrumented with four thermocouples

to monitor the duct air temperature. Each flexible

connector assembly was instrumented with 20 thermocouples.

These were distributed as follows: 2 on the flexible

5
connector under the insulation inside the furnace; 2 on

the flexible connector outside of the furnace; 12 on the

terminal unit; one in the airstream where the connector

was attached to the terminal unit; 2 at the air inlet

of the architectural enclosure; 1 in the air outlet; and

1 on top of the enclosure. The thermocouple layout is

shown in Figure 9. These thermocouples were chromelalumel, type K, 24 gage.

The temperatures were recorded on both a paper tape

temperature recorder and on a printing data logger. The

paper tape data was transferred to a magnetic tape for

processing with the NBS computer system.

[61

In accordance with the requirements of NFPA 90A the

tests were run without air flow in the system.

3.0 EVALUATION TEST

3.1 Description of Test (NBS Test 516)

In this test four 18 inch diameter main ducts were hung

from the furnace closure. One connector was attached to

each duct. Figure 10 shows the test layout in the

furnace.

'-

... J

Two non-metallic commercially available connectors, consisting

of a 5 inch dia. glass fiber and a 5 inch dia. woven glass fiber

6
fabric, were each attached from separate ducts to a simulated

box type terminal unit and architectural enclosure similar to

that used in the pilot test. Two metallic connectors, 5 inch

dia. and 6 inch dia. galvanized steel, were each attached

from separate ducts to a terminal unit similar to that

used in the One New York Plaza Building at the time of

the fire in August 1970. The architectural enclosures for

these building terminal units (hereafter referred to as the

ONYP terminal units) were sized to provide reasonable

clearances and approximately the same volume as those

for the box type units. The volume of the architectural

enclosures for the ONYP units was 25 cu. ft. while that ,

for the box units was 2A.75 cu. ft. Figure 11 shows the

construction details for the fiber glass flexible

connectors and Figure 12 shows the details for the

steel flexible connectors.

The tests with the non-metallic flexible connectors and

box type terminal units were similar to those in Test 512,

except that round duct was \:sed in Test 516. The tests

cannot be directly compared because of interaction effects

that developed in Test 512.

As in Test 512 there was no air flow in the assembly.

7
3.2 Furnace Closure

The furnace enclosure was identical to that in the pilot test.

The penetrations through the furnace closure were altered

from that used in the pilot test. The hole through the

closure was only slightly larger than the connector and

because of this tight clearance no glass fiber was packed

into the space around the connector. On the fire side, the

hole was blocked with a steel flange plate. The plate for

the 6 inch diameter steel connector, which was supplied by

the manufacturer of the flexible connectors, was made of

stamped 19 gauge steel. The plates for the 5 inch diameter

connectors were fabricated at NBS of welded 16 ga. steel.

For the glass fiber duct, a suitable flange plate was unavailable

at the time of the test so the hole around the duct was packed

with glass fiber and was protected with vermiculate plaster on

the fireside. Figure 13A shows the welded flange plate and

Figure 13B shows the pressed steel flange plate. Figure 14A and

lAB show the penetrations through the furnace closure for the

steel and felted glass fiber connectors, respectively.

3 . 3 Flexible Connectors

The four connectors consisted of:

1. 5 inch inside diameter, 1 inch thick, felted glass

fiber wrapped around a steel wire spiral and covered

with a vinyl plastic cover.

8
2. 5 inch inside diameter woven glass fiber, neoprene

impregnated, wrapped around a wire spiral.

3. 5 inch inside diameter galvanized steel, average

wall thickness = .005 in.

4. 6 inch inside diameter galvanized steel, average

wall thickness = .005 in.

For this test the attachment of the steel connectors to the

main ducts was changed to represent a common field type, as

shown in Figures 12 and 15. Instead of using a flanged plate on

the duct a small hole was cut in the duct and radial cuts

were made from the edge of the hole out to the radius of the

connector and the resultant strips were bent out to form ears.

The connector was attached to the ears with a steel friction

band. In addition to the bands, four self threading sheet

metal screws were used to attach the connector to the bent

out ears.

As in the pilot test, the main ducts were covered with a

rated two inch thick aluminum foil-backed glass fiber

blanket. This was attached with a rated adhesive and

rated tape, see Figure 15.

Within the furnace both the woven glass fiber connector, and

the steel connector were wrapped with a 1 inch thick glass fiber

and covered with a vinyl plastic cover, which was supplied

9
by the manufacturer of the flexible connectors. As in the

pilot test, the main ducts and the connectors were painted

with a rated vapor barrier. See Figures 14A and 14B.

3 . 4 Instrumentation

3.4.1 Glass Fiber Connectors

The glass fiber flexible connectors were each instrumented

with 19 thermocouples distributed in the following way:

2 inside the main duct*, 4 on the surface of the main

duct, 2 on the duct hangars, 2 on the connector under the

vinyl cover for the felted connector inside the furnace,

2 on the connector outside of the furnace, 1 at the inlet

to the terminal unit, 2 at the outlet of the terminal unit,

2 in the inlet of the architectural enclosure and 2 in the

outlet of the architectural enclosure. The thermocouple

details for the glass fiber connectors assemblies are shown

in Figure 11. The thermocouples were 24 gage, chromel alumel

(type K).

3.4.2 Steel Connectors

For the steel connectors, 21 thermocouple channels were used.

The only differences in arrangement were on the ONYP terminal

unit where 3 thermocouples were placed on the discharge

compared with 2 on the box units and an additional thermo-

—

Thermocouples 14A and 14B, and 15A and 15B were connected in parallel.

IG
couple was placed on the cold side inlet valve of the

terminal unit. The thermocouple details for the steel

connectors assemblies are shown in Figure 16.

4.0 TEST RESULTS

A.l Pilot Test (NBS Test 512)

Since all the connectors were connected to the same main

duct, after the failure of the first connector, cross

current drafts were introduced which prevented the collection

of meaningful temperature data. For this reason no temperature data for test 512 are included in this report.

These interaction effects indicate that in a system in a

"shut down condition" smoke and hot gases can easily enter

and be distributed throughout the system.

4.1.2 General Observations

After 6 minutes of test the aluminum connector melted.

The steel flexible connectors remained intact until they

separated from the duct at 89 minutes.

4.2 Evaluation Test (NBS Test 516)

In this test employing independent ducts, interaction effects

resulting from the failure of any one connector were eliminated.

The results for the glass fiber connectors and the steel

connectors will be discussed separately.

11
4.2.1 Temperature Observations

4.2.1.1 Furnace Temperatures

The furnace temperatures were measured with 12 shielded

thermocouples which were in accordance with the requirement of ASTM E 119. The furnace temperature followed

the standard curve of ASTM E 119 closely and no correction

was needed. The average furnace temperatures are shown in

Figure 17.

4.2.1.2 Connector Assembly Temperatures

The temperatures for the assemblies are shown in Figures 18

to 30 on four sets of three graphs, and a summary graph.

The first graph of each set shows the temperatures from the

main duct to the inlet of the terminal units. The second

graph shows the temperatures from the inlet of the terminal

unit to the outlet of the architectural enclosure, and the

third graph shows only the inlet and outlet temperatures at

the architectural enclosure. Figure 30 compares the outlet

temperatures of all four architectural enclosures.

4.2.1.3 Glass Fiber Connectors

A comparison of the temperature records for the felted

glass fiber assembly (Figures 18, 19, and 20) with

those for the woven glass fiber fabric assembly (Figures 21,

22, and 23) suggests that there was no great difference in

the temperature performance of the two non-metallic

12
connector assemblies. The visual observations during and after

the test indicate that the woven glass fiber fabric assembly was

marginally superior.

During the test both glass fiber connectors had melted inside

the furnace by about 15 minutes of test time. The woven

fabric connector however maintained some structure until

about 23 minutes of test time. Outside of the furnace the

woven fabric connector maintained enough structure to contain

the hot gases for the full period of the test, while the felted

glass fiber connector melted above the furnace closure and it

was necessary to block off this penetration at 41 minutes

of test time. Before blocking off the penetration of

the felted fiber glass connector, the air inlet temperatures

at the terminal unit were similar for both of the non-metallic

connectors

.

It should be emphasized that in this test there was, in

general, very little air movement from the furnace

through the opening in the connectors. This is because

the NBS test furnace, like most floor test furnaces,

operates under neutral to slightly negative pressure. In

an actual fire situation, the hot gases would probably be

under slight positive pressure and so air movements through

openings in the connectors and around the connector penetrations would be relatively more serious than occurred in

this test when the non-metallic connectors failed.

13
4.2.1.4 Steel Connector Temperatures

Comparing the temperatures of the two steel connector assemblies, in Figures 25 to 28, it is seen that from about

30 minutes to the end of the test the inlet temperatures

to the terminal unit for the 5 inch connector are about

675°C while those for the 6 inch connector are about 500°C.

During the test it was observed at 32 minutes that the

5 inch connector was separating from its duct. However,

the abrupt rise in temperature at the outlet of the

architectural enclosure would indicate that the separation

probably occurred at about 20 to 25 minutes. This

separation which is shown in Figure 31 allowed hot

furnace gases to enter this assembly and so produce the

higher observed temperatures in the 5 inch connector assembly.

4.2.1.5 Comparison Data

In Figure 30 the outlet temperatures above the four

architectural enclosures are compared. The rise in temperature, at the outlet of the 6 inch galvanized steel assembly,

at the end of one hour is below the allowable temperature

rise of 139°C which is usually taken to represent the

temperature transmission limit. The 5 inch assembly

exceeded the 139°C rise because the connection opened

up, showing that the connector assembly was governed by

its connection. The pilot test (NBS test 512) showed

that a flanged connection could remain intact for this

period.

14
5.0 DISCUSSION AND SUMMARY OF RESULTS

5 . 1 Temperature and Fire Endurance

The two tests studied the effects of fire breaking into an

HVAC assembly through the flexible connectors. Since the

flexible connector penetrates a fire-rated floor assembly,

its construction should provide equivalent protection

against fire transmission. The criteria of failure used in

these tests are based on the ASTM E 119 (7) criterion for

temperature transmission - the rise in temperature should

not exceed 139°C nor should there be any flame transmission.

The temperature rise criterion was applied to the temperature

on top of the architectural enclosure. The criterion was

applied at one hour, consistent with a fire duration based on

the expected fire load in an office building.

The tests showed that the criterion could be met if the fire

did not enter the flexible connector, the main duct, or any

part of the HVAC system. Since a connector must maintain its

integrity against fire penetration, the method of attaching

the connector to a main duct and the fire stopping around the

penetrations through a fire barrier must also be able to withstand the temperature for the required fire exposure period.

The pilot test showed that a flanged fitting to the

main duct kept the steel connector attached. In the

15
second test, using a field type of attachment one steel

connector held and one separated from the main duct.

The behavior of the 5 inch galvanized connector in the

second test, showed that if the method of attaching the

connector to the main duct allows the joint to open up,

the transmitted temperatures will be similar to those

of a non-metallic duct or of a low melting point metal duct.

The steel connector when properly attached prevented the

fire from entering the system and heating the architectural

enclosure above an allowable limit.

It is emphasized that the performance reported assumes only a

very low to zero flow in the HVAC system, consistent with the

supply air in the fire area being shut down in accordance with

NFPA standard 90A.

5 . 2 Smoke and Toxic Gases

During the early part of the evaluation test, moderately

dense and irritating smoke came out of all four assemblies.

As the test progressed the amount of smoke decreased. A

qualitative comparison is shown in Figure 32.

In the non-metallic assemblies the smoke and irritating

gases probably came from the resin and plastic in the

glass fiber, while in the steel assemblies it may have

16
come from the rubber fittings and the impregnated glass

fiber air filter in the ONYP terminal units. A comparison

of the charring of the filters in the terminal ONYP units is

shown in Figure 32.

Though this investigative program was primarily concerned with

the fire resistance of flexible connector assemblies, the

observed smoke development during the test indicate the

need for additional research to develop criteria for

measuring and limiting the amount of smoke generated by

materials in these assemblies.

5 . 3 Comparison of Square and Round Ducts

The two tests provided an opportunity to compare, in a subjective way, the performance of square and round ducts.

During the pilot test with square ducts, the glass fiber

wrapping separated within a few minutes allowing the furnace

heat to impinge directly onto the full length of the duct. As

the test progressed the sides of the duct tended to buckle,

reducing the height of the duct, and thus reduce the bending

stiffness* of the duct faster than the reduction in strength

due to heating alone.

Bending stiffness is proportional to the square of the depth.

17
With the circular ducts , the insulation remained in place

for approximately 15 minutes, protecting the duct from

the direct furnace heat for this period. As the test

progressed the ducts tended to flatten in a horizontal

direction, that is, the vertical sides moved towards

each other, decreasing the horizontal diameter of the

duct. This type of deformation would tend to keep the

bending stiffness proportional to the heated strength

of the duct metal.

The tests suggest that a round duct may maintain its

structural integrity better than a square duct under

a fire exposure. It should be noted however that the

test did not include any comparison of joint strength or

span lengths both of which affect performance. The

relative strengths of round and square ducts and the

factors affecting the performance of round ducts can

only be determined by further tests.

5 .A Performance Considerations

If the following conditions are met:

Element or Assembly Required Performance

flexible connectors do not melt

do not pyrolize

joints remain intact

remain tight

18
HVAC system shut down

Then, the flexible connector assembly will keep the fire out of

a compartment, and the temperatures in the compartment may

remain low enough to prevent ignition of combustibles in the

room above.

For life safety an additional requirement is that the terminal

unit does not contain materials that will degrade under heat

and give off excessive smoke and noxious gases. Possible sources

for these include binder and impregnates in the air filter,

rubber and plastic inserts and baffles (see paragraph "5.2 Smoke

and Toxic Gases")

.

Though these requirements may seem self evident they are

more restrictive than those required under NFPA 90A [6].

6.0 ACKNOWLEDGEMENT

This research was supported in part by a grant from the American Iron

and Steel Institute.

19
APPENDIX A

Summary of Observation Made During Pilot Test (NBS Test 512)

Test Time Observation

Hrs:Min

00:02 The Insulation on the bottom of the main duct

has separated from the duct and is hanging down

from one edge.

00:05 ' Smoke coming out of architectural enclosures.

00:06 The aluminum connector has melted.

00:14 Insulation on the main duct is essentially destroyed

at this time. Insulation on the A and 6 inch

galvanized steel connectors is still partially

intact. The insulation is melting in place rather

than falling off into the furnace.

00:21 The A inch steel connector is a dark color while

the 6 inch steel connector is glowing a dull red.

00:35 Main duct starting to deform in an accordian

manner.

00:43 Some smoke still coming out of the architectural

enclosure of the 6 inch steel connector assembly.

00:50 Both steel connectors are glowing red.

00:54 Flange connections holding up quite well.

01:05 Two technicians checking the 4 inch galvanized duct

for obstruction. No obstructions found.

01:29 Six inch connector has separated from main duct.

20
01:32 Four inch connector has separated from main duct,

01:42 End of Test.

21
APPENDIX B

Summary of Observations Made During Evaluation Test (NBS Test 516)

Test Time Observations

Hrs:Min

00:02 The insulation has come off both the 5 inch and

I- 6 inch steel flexible connectors. (Note that

this was applied by NBS prior to test)

.

00:03 Air is coming out of all four architectural

enclosures. (This was checked with a piece of

thin aluminum foil hung from a rod which indicates

that there is air movement) . There is also moderately

dense smoke coming out.

00:05 The insulation around the main ducts appears to be

smoking and flaming.

00:07 Smoke is still coming out of each one of the

architectural enclosures. The smoke seems to be a

little denser from the two glass fiber connectors

assemblies. Smoke at the top of the furnace is

acrid and it is difficult to stay up there for more

than a few minutes, and it has partially obscured

vision across the top of the furnace. See Figure 31

showing the smoke conditions at the top of the

furnace.

The insulation is staying in place even though its

deteriorating from the heat. The insulation on the

22
main ducts has split. The splits are circumferential

and are about 3' long.

The insulation is starting to fall off the main

duct, it is falling off in pieces and appears to

be deteriorated at this time. The smoke is still

coming out of the architectural enclosures.

The neoprene fabric connectors continues to show

some structure.

The remnants of the glass fiber insulation around

the main ducts continue to fall into the furnace.

The parts of the main duct that are visible show

some localized buckling. The glass fiber is dripping

and melting into the furnace.

The neoprene impregnated woven fiber glass flexible

connector at the south east corner has fallen in.

Referring to the two steel connectors at the center

of the furnace, the main ducts appear to be collapsing

and pulling away from the connectors. Both these

ducts seem to be collapsing in sort of a vertical

plane and pulling away from the connectors and there

seems to be some deteriorating at the junction point.

The architectural enclosure attached to the glass fabric

connector has no air coming out of the top. At the

assembly with the glass fiber connector there

is air coming out of the architectural enclosure.
The 5 inch steel connector has separated from its

connection at the main duct, though it is still

hanging in place. See Figure 33.

The architectural enclosure connected to the

woven glass fiber connector now has air flowing

out of it again. The main ducts are starting to

deflect significantly. It would say that they have

all deflected about 5 or 6 inches.

On the top of the enclosure where the standard

glass fiber duct connector is located it is necessary

to put a cap over the hole where the flexible

connector comes through. Too much heat is coming

through and it may ignite the closure.

The smoke has abated but there is still smoke coming

out through the two architectural enclosures that

are attached to the steel connectors, visibility

is fair. The furnace closure is charring and

smoking a little.

The 6 inch galvanized steel flexible connector

is still in place.

The roof closure is starting to burn through; the

crackling sounds have become quite severe. The

6 inch galvanized steel flexible connector is still

intact.

Gas off. Fire was breaking through the furnace

closure. End of test.

24
BIBLIOGMPHY

1. J. A. Wilson and J. J. Capron

"The Fire Hazard of Fibrous Glass Ducts - An Evaluation,"

Fire Technology . Vol. 2, No. 1, Feb. 1966, pp. 24-36,

National Fire Protection Association, Boston, Massachusetts.

2. A. F. Roberts, G. C lough, and J. R. Blackwell

"A Model Duct for Mines Research," Safety in Mines Research

Establishment Research Report No. 243, Dec. 1966, Sheffield,

England

.

3. A. F. Roberts and G. Clough

"The Propagation of Fire in Passages Lined with Flanmiable

Material," Combustion and Flame , Vol. II, No. 5, October 1967,

pp. 365-376, Butterworths , London, England.

4. W. Robert Powers

"Report of Fire at One New York Plaza, New York, N.Y.", The

New York Board of Fire Underwriters, Bureau of Fire Prevention

and Public Relations, 1970, New York, N.Y.

5 . Anonymous

"Low Velocity Duct Construction Standards" - 4th Edition, Sheet

Metal and Air Conditioning Contractors National Association, Inc.

(SMACNA), 1969, Washington, D.C.

25
Anonymous

"Installations of Air Conditioning and Ventilation Systems 1971,

NFPA 9 OA , National Fire Protection Association International,

Boston, Massachusetts.

Anonymous

"Standard Methods of Fire Tests of Building Construction and

Materials," Designation E 119, American Society for Testing and

Materials, Philadelphia, Pennsylvania, 1971.

26

Figure 2 - Test 512- Side o£ Raised Furnace Closure
Figure 3 - View of Steel Connectors Showing the Vinyl Covering and the

Method of Attaching to the Tiuct.
Figure 4 Test 512 View of Aluminum Connector Attached to

the Main Duct

Figure 6 Test 512 - View of Aluminum Flexible Connector at Terminal

Unit
1

Figure 7 - Test 512 - Architectural Enclosure in Place
Figure 8 - Test 512 - Aluminum Flexible Connector. (Note

.

, method of blocking penetrations through

closure)
3o>-<

LUI Q-ouO

:^

lUX

I—

LUO

LU

IDo
llJ o<

Li.

\-O

Z)Q

cnOoo

aN3 HldON


Figure 13 Flange Plates

Figure 15 Typical Duct Showing Glass Fiber Blanket and Connector

Junction Point
s<

UJ

a:
1500

1450_

1400_

1350_

1300_

1250_

1200_

1 150_

U00_

1050_

1000_

950_

900_

850

800_

750_

700_

650_

600_

550_

500_

450_

400_

350_

300_

250_

200_

150_

100_

50 _

0

0

m flVERRGE FURNRCE TEMPERRTURE

- STRNORRD El 19

10 20 30 40 Eo &0

^

TIME - MINUTES

"So So T&o no Tko

FIG. 17 TEST 516 FURNACE TEMPERATURES
see Figure 16 for locations X T/C 4

<!> T/C 5 INLET RIR TEMPERRTURE TO TERMINRL UNIT ^ T/C 14 S, 15 RVE. INTERIOR TEMP. MRIN DUCT

10 ^0 5o 40 So So 'to So §0 rEo no ilo

TIME - MINUTES

FIG. 18 TEST 516 5 INCH GLASS FIBER - TEMPERATURES ALONG CONNECTOR
1000_,

O T/C 5 INLET RIR TEMPERRTURE TO TERHINRL UNIT

A T/C 6 4 7 MAX. 0UTLET RIR TEMPERRTURE EROM TERhlNRL UNIT 3au_ ^ T/C 8^9 MAX. INLET RIR TEMPERATURE TO RRCHI TECTURRL ENCLOSURE

X T/C 10 «. 11 MRX. OUTLET RIR TEfiPERRTURE FROM RRCH I TECTURRL ENCLOSURE

900-

850_

800_

750_

TIME - niNUTES

FIG. 19 TEST 516 5 INCH GLASS FIBER - TEMPERATURES ALONG TERMINAL UNIT

AND ARCHITECTURAL ENCLOSURE
500_

450_

400_

350_

UJo

300_

Z50_

Q. zoo_

150_

100_

50 _

O T/C 10 «. U MRX. OUTLET filR TEMP. ARCH. ENCLOSURE

A T/C 8 4 9 MRX. INLET filR TEMP . ARCH. ENCLOSURE

To ^0 ^0 40 io &0 ^70 So So lEo no I'zo TIME - MINUTES

FIG. 20 TEST 516 5 INCH GLASS FIBER - AIR TEMPERATURES ARCHITECTURAL ENCLOSURE
see Figure 16 for locations

O T/C 1 A T/C Z X T/C 4

<!> T/C 5 INLET RIR TEhFERRTURE TO TERfllNRL UNIT ^ T/C 14 S, 15 RVE. INTERI0R TEnP . HRIN DUCT

Yo ^0 5o 40 Eo fo "to So So i"5o no ilo

TinE - MINUTES

RG. 21 TEST 516 5 INCH WOVEN GLASS FABRIC - TEMPERATURES ALONG CONNECTOR
1000

© T/C 5 INLET flIR TEMPERRTURE TO TERniNflL UNIT

Q-f^ A T/C 6 * 7 MRX. OUTLET flIR TEMFERRTURE FROM TERMINRL UNIT 30U_ ^ T/C 8 ^ 9 nflX. INLET fllR TEMPERRTURE TO RRCHI TECTURRL ENCLOSURE

X T/C 10 ^ 11 MAX. OUTLET RIR TEMPERRTURE FROM RRCH I TECTURRL ENCLOSURE

900_

850-

800_

750_

700_

650- ^ 600_ ^ 550_

TIME - MINUTES

FIG. 22 TEST 516 5 INCH WOVEN GLASS FABRIC - TEMPERATURES ALONG TERMINAL UNIT

AND ARCHITECTURAL ENCLOSURE
500

CD T/c 10 4 11 nnx. outlet rir temp. arch, enclosure

A T/C 8 9 fIRX. inlet flIR TEnP . ARCH. ENCLOSURE

0 10 ^0 5o 40 Si Si "to So S TEo iTo ilo

TIME - MINUTES

23 TEST 516 5 INCH WOVEN GLASS FABRIC - AIR TEMPERATURES ARCHITECTURAL ENCLOSURE
see Figure 16 for locations

12

3

d

5 INLET flIR TEHPERRTURE TO TERniNflL UNIT - HOT SIDE

6 INLET TEMPERATURE flT TERMINAL UNIT- COLO SIDE (SHUT)

16 4 17 AVE. INTERIOR TEMP- MAIN DUCT

To ^0 5o 40 io ^0 ^0 So So TEo no 1^20

TinE - MINUTES

FIG. 24 TEST 516 5 INCH GALV STEEL - TEMPERATURES ALONG CONNECTOR
T/C 5

T/C 6

INLET flIR TCMPERflTURE TO TERMINRL UNIT HOT SIDE

INLET niR TEMP. RT TERIIINflL UNIT CQLD SIDE (SHUT)

NflX. OUTLET flIR TEhPERRTURE FROM TERHINRL UNIT

11 RVE. INLET RIR TEMPERRTURE TO RRCH I TECTURRL ENCLOSURE

13 nflX. OUTLET fllR TEMPERRTURE FROM RRCH I TECTURRL ENCLOSURE

0 To fo S 40 Eo &0^

&0 So TEo no ilo

TIME - MINUTES

FIG. 25 TEST 516 5 INCH GALV STEEL - TEMPERATURES ALONG TERMINAL UNIT

AND ARCHITECTURAL ENCLOSURE
500^

450_

400_

350_

o

CD

300_

250_

=>

*-

200.

z:UJ

150_

100_

50 _

© T/C 12 ^ 13 n«X. OUTLET RIR TEMP. RRCH . ENCLOSURE

A T/C 10 «. 11 AVE INLET flIR TEtIP • RRCH. ENCLOSURE

To ^0 5o 40 ^0 "to &o So ito no 1^20

TlhE - MINUTES

FIG. 26 TEST 516 5 INCH GALV STEEL - AIR TEMPERATURES ARCHITECTURAL ENCLOSURE
see Figure 16 for locations

INLET RIR TEriFERRTURE TO TERfllNflL UNIT - HOT SIDE

INLET TEriFERRTURE RT TERMINRL UNIT - COLD SIDE (SHUT)

(, 17 RVE. INTERIOR TEMP- MRIN DUCT

0 10 20 30 40 "^0 60 ^0 So So TSo 110 l20

TIME - MINUTES

FIG 27 TEST 516 6 INCH GALV STEEL -TEMPERATURES ALONG CONNECTOR
1000

950_

900_

850-

800_

750_

700_

650_

600_

S 550J

500_ ^ 450.

UJ^ 400.

350.

300.

250.

200.

150.

100.

50 .

0

+X

T/C 5 INLET RIR TEfiPERflTURE TO TERMINflL UNIT HQT SIDE

T/C 6 INLET flIR TEMPERATURE flT TERHINRL UNIT CQLD SIDE (SHUT)

T/C 7.8^ 9 tIRX. 0UTLET RIR TEMFERRTURE FROM TERMINRL UNIT

T/C

T/C

10

12

11 RVE INLET RIR TEhPERRTURE TQ RRCH I TECTURRL ENCLOSURE

MRX. OUTLET RIR TEHPERRTURE FROh RRCH I TECTURRL ENCLOSURE

10 To S

T

Jo So 60

TiriE - MINUTES

'to So 5o Tfo Tio ilo

1

FIG. 28 TEST 516 6 INCH GALV STEEL - TEMPERATURES ALONG TERMINAL UNIT

AND ARCHITECTURAL ENCLOSURE
500

450_

400_

350_

300_

UJa

Z50_

UJoc

I—cc^ 200.

150_

100_

50 _

© T/C 12 «, 13 MRX. OUTLET RIR TEtiP . RRCH . ENCLOSURE

A T/C 10 4 11 AVE. INLET FlIR TEfiP . ARCH. ENCLOSURE

To fo~ "To ^0 'to So So ilio no ilo

TIME - MINUTES

FIG. 29 TEST 516 6 IN GALV STEEL -AIR TEMPERATURES ARCHITECTURAL ENCLOSURE
500_

il50_

400_

350_

300_ o

Ui

o

250.

UJQC

»—cr

1 1 f Q_ ZOO.

c

UJ

150_

100_

50 _

o T/c 10 <. 11 nnx. 5 IN glass fiber

A T/c 10 4 11 MRX. 5 IN WOVEN GLASS FABRIC

+ T/C 12 <, 13 fIflX. 5 IN GflLV STEEL

X T/C 12 <, 13 MRX. 6 IN GRLV STEEL

0 To ^0 5o 40 io ^0 "to &o &o TEo no Ho

TinE - MINUTES

FIG. 30 TEST 516 COMPARISON OF OUTLET AIR TEMP. ON ARCH. ENCLOSURES
Figure 31 - Separation of 5 inch Steel Connector from Main

Duct
m

0) p

•Heo p

<D 71 -P CDo 0 w g

CO t-l

ClJ 1 f-. ^3 Po

CD P

•H

DOO

•H ^

Uh <

CM

CO

5h

tn p

•H


NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSIR 73-267

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Report of Fire Tests on Flexible Connectors in HVAC Systems

5. Publication Date

6. Performing Organization Code

7. AUTHOR(S)

Lionel A. Issen

8. Performing Organ. Report No. NBSIR 73-267

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 4619360

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP) 13. Type of Report & Period Covered

Final Report

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

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

bibliography or literature survey, mention it here.) The contemporary high rise building with its control air conditioning system and high

content of synthetic materials presents a higher hazard than those erected prior to

1950. The ability of the duct work to resist fire breaking into it and spreading

through the duct system is an important factor affecting the integrity of the building.

Since they penetrate fire barriers, the flexible connectors between the main ducts and

the terminal units are important elements in maintaining the desired fire resistance.

Flexible connectors made of four different materials (aluminum, galvanized steel,

felted fiberglass and woven fiberglass fabric) and two attachment techniques were subjected to fire tests in accordance with ASTM E119. The results show that the materials

of the connectors must withstand the fire exposure, the connectors must remain tightly

attached to the main duct, and the penetrations through the fire barrier must be suitably blocked in order to prevent fire from breaking into the duct system. The tests

also showed that rubber and plastic materials in the terminal units can produce significant amounts of irritating smoke.

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) Aluminum; ductwork; fabric; fiberglass; fire tests; high rise

buildings; HVAC systems; steel; terminal units.

18. AVAILABILITY 2j Unlimited

1

' For Official Distribution. Do Not Release to NTIS

1

^ Order From Sup. of Doc, U.S. Government Printing Office Washington. D.C. 20402. SD Cat. No. C13

1 1 Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

21. NO. OF PAGES

56

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Price

USCOMM-DC 29042-P74