The Fire Hazard Associated with Plastic Drain and Waste Pipes in High Buildings

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Publisher’s version / Version de l'éditeur:

Technical Note (National Research Council of Canada. Division of Building

Research), 1969-04-01

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The Fire Hazard Associated with Plastic Drain and Waste Pipes in High

Buildings

McGuire, J. H.

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DIVISION OF BUILDING RESEARCH

NATIONAL RESEARCH COUNCIL OF CANADA

'JI'

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JHI

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NOTlE

No.

535

PREPARED BY _{J. H. McGuire} CHECKED BY _{G. W. S.} APPROVED BY N. B. H.

April 1969

PREPARED FOR Inquiry and record purposes.

SUBJECT _{THE FIRE HAZARD ASSOCIATED WITH PLASTIC DRAIN AND WASTE}

PIPES IN HIGH BUILDINGS.

Drain and waste pipes sometimes penetrate partitions (e. g. walls

and floors) that are intended to have a certain fire resistance. It is at

these breaks in the continuity of fire-resistant partitions that the greatest

hazard in the use of plastic pipe can arise. Where iron pipe is used it

generally remains in place during the cour se of a fire and temperature s capable of igniting combustible materials are not likely to be found beyond the immediate vicinity of the partition.

MISCELLANEOUS TEST INFORMATION

Various tests (1,2) have shown that where appropriate pressure

differentials exist, ｦｩｾ･ on one side of a partition that is penetrated by a

plastic pipe will at some time give rise to unacceptably high temperature s

or to the flow of hot gases at the far side of the partition. During tests

carried out in the Netherlands with pipes of 4-in. diameter, hazardous conditions developed within 10 minute s.

Ad hoc tests carried out by the Fire Research Section, DBR/NRC indicated that fire would propagate up a 4-in. diameter pipe of a material

(PVC, CSA Grade II) with an E 162 flame -spread rating of only 7. A

natural gas burner was located at the bottom of a 5-ft length of pipe held

vertically. With asbestos cement pipe flaming was confined to the region

of the burner; with the PVC pipe, flames issued from the top of the pipe

within 15 seconds of igniting the burner. On removing the burner all

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- 2 ...,

It is apparent that, given appropriate draught conditions, the penetration of a fire partition by virtually any combustible pipe of a few ｩｉｾ｣ｨ･ s or more diameter can be a hazard.

HAZARDS IN A HIGH-RISE BUILDING

Unfortunately in a high building almost any pre s sure differential

within the range ±0.05 in. of water can be found across one or another

fire partition. Where pipes are installed in a vertical service shaft,

with connections at every storey, the whole range of pressure differentials

will probably be encountered across the shaft boundaries. Figure 1 and

Table 1 illustrate, respectively, typical flow patterns and values of

pressure differential that one might encounter within a high building in the depths of winter.

From information such as that given in Figure 1 and Table 1 assessments can be made of the hazards associated with the use of

plastic pipes in various locations. The first case that can be readily

discussed is that of the vertical pipe penetrating several floors in the

building. Regardless of how severely it is penetrated by fire tle

additional leakage areas created will not seriously interfere wi h the over -all air flow pattern in the building which will remain sub s anti ally

as illustrated in Figure 1. A positive pressure differential betreen the

fire floor and the floor above can thus be expected, in the first ｾｮｳｴ｡ｮ｣･Ｌ

regardle s s of the location of the fire. This differential will in act be

slightly accentuated by the expansion process to be expected as tempera-tures rise in the fire compartment.

Two interesting variations of the above conditions can

exterior windows on the fire floor are fractured and fall out. s suming

that all door s in fire partitions within the building are closed, tl e opening to the exterior constituted by broken windows could be consider) d large

in comparison with the aggregate of leakage areas to the rest 0 the

building. The fire compartment can then be considered to be a the sam.e

pressure as the exterior at that height. As a first approximati,n all

other pressures can be considered substantially unchanged. Were the

fire compartment is at a low level in a building, a pre s sure dif erential of 0.2 in. of water could be driving hot gases and flames throu h openings

communicating to the adjacent floors or shafts. If the fire wer at a high

level, window breakage would give the reverse of the condition just

de scribed and all openings between the fire area and the remaiI der of the building would deliver air to the fire area.

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3

-It is thus apparent that the penetration of floor s by plast c pipe s

of any appreciable diameter, particularly at a low level in a ｨｩｾｨ building,

can permit transDl-is sion of a fire acros s a fire partition.

Where vertical pipe runs are confined to shafts with horrzontal connecting runs at every floor, considerations such as those jurt mentioned show that fire at a low level in the building would give risk of tvansmission of fire to the shaft. Similarly, fire in the shaft would give risk of fire· in

high level floor areas. The risk of fire at a low level being tra smitted

to the shaft would be accentuated by the pos sibility of window breakage re sulting from the fire.

PRECAUTIONARY MEASURES

From the foregoing it would seem unwise to permit unprotected large-dianleter plastic pipes to penetrate fire-resistant floors lt least

at low levels in a high-rise building. Above the level of the int

nor-exterior neutral pressure plane (usually about half-way up a building) it nlight be sufficient to rule that the nlaterial be not highly flacl.nlable, that the pipe dianleter be no greater than 4 in., and that for dis' ance s of 20 in. above and below every floor penetrated, pipes of dianl ter larger than I in. should be protected by sheet iron or steel sle9ving.

Many vertical service shafts contain sufficient cOnlbusti Ie

nlaterials to pernlit quite rapid development of a fire even prio to the

installation of plastic drain, waste and vent pipe s. Re strictions on the

combustibility or flamnlability of plastic pipes need not

ｴｨ･ｲ･ｦｯｾ･

be

associated with this feature. They nlight be based on a desire firstly

to linlit the over -all fire load in the shaft and secondly to incre se the energy required to produce an ignition in the shaft.

1£ the fire re sistance of the shaft walls and closure s is substantial, it is probably not necessary to linlit the fire load in a service

ｳｾＧｬ｡ｦｴＮ

Provided arrangem.ents are nlade to vent a shaft adequately, it tis unlikely that a fire would be of long duration and nlany fornls of construction

would contain it. It should be appreciated, however, that rega dless of

its duration the fire can be expected to be intense and that tenlp'erature s will be higher than custonlary.

Reducing the flanlnlability with a view to reducing the li <elihood

of ignition is advantageous. The most probable source of ignit' on is an

electrical fault. If, however, the electrical de sign engineer has made

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-.. n'lay be low. Materials with E84 or E162 ratings of several hu dred

(e. g. acrylonitrile - butadiene - styrene and -untreated soft

ｦｩ｢ｲ･｢ｾ｡ｲ､Ｉ

can be readily ignited with a n'latch, whereas a n'laterial such as treated PVC) with an E 162 rating of only 7, requires a substantial ignition source and will, in fact, only continue to burn with some level of support dependent on the geometry involved.

Horizontal connections to the vertical pipe require sUbsjantial

protection both at low levels (to prevent fire in a floor area from

penetrating the shaft) and at high levels (to prevent fire in a shaft from

causing ignitions in all the upper storeys). In the absence of inlformation

gained from te sts involving appropriately adver se pres sure

､ｩｦｾｬ･ｲ･ｮｴｩ｡ｬｳＬ

it is not possib.le to say whether the partial protection of such b!orizontal runs by iron or steel sleeves would be adequate. It can be ｳｵｧｾ･ｳｴ･､Ｌ

however) that sleeve protection of the whole length, between s aft wall and water trap, would probably be adequate provided the flammability of the pipe material were not excessive.

SUMMAR Y OF CONCLUSIONS

l) Pipe s of quite low flammabilitie s will permit. fire to

propagate vertically within them.

the

I

case

I

a) where a vertical pipe-run penetrated floors, in which principal hazard would be to the floor above and

2) Particularly high pressure differential (of order 0.2 in. W G.)

could give rise to undue hazard in a high building as a result of the

use of plastic pipes if fire occurred in a vented compartment a a low

level in a building. The fire might itself create vents to the ex erior

by causing window breakage. The hazard would arise:

b) where a connection to a vertical shaft occurred, in whi h case transmission of the fire to the shaft might result.

3) It would seem unwise to permit unprotected large -diamete . plastic

pipes to penetrate fire-resistant floors at least at low levels in a high-rise building.

At high levels, pipes of diameter no greater than 4 in. ight be

allowed to penetrate fire -re sistant flbor s provided that, where they were of diameter greater than lin.) they were protected by sheet ir n or steel sleeving for distance s of 20 in. above and below the floor

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-... 4) Where plastic pipes penetrated a shaft boundary below the evel

of the neutral plane, substantial protection would again be calle for

and partial protection over a limited length might prove insuffi ient. At high levels there is greater prospect that partial protection

horizontal branch pipes might prove adequate.

5) Where plastic pipes are to be installed in vertical shafts, educing

their flammability with a view to reducing the likelihood of ignition is advantageous.

REFERENCES

1. van Sante, F. J. Results of fire tests on plastic pipes nd

sheets for covering walls and ceilings. Foundation Rati bouw,

Rotterdam, Holland.

2. Fire tests with plastic tubes carried out at the Researc Station

in Studsvik, Spring 1963. National Swedish Institute for Building

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"

Outside -

OaF

ｌＸ｡ｫｱ｛ｾＭＭＭｩ｜ｲ｣｡ｳＮＮｊｬ･ｾｾｾｯｲｇｙ

:

exterior wall - 2.50 sq ft

shaft

- 5.00 sq ft

floor

-

3.75 sq ft

;

-I

_r

Outside

Vjall

_{Vertical Shaft}

Between Floors

Floor

6P

IMass Flow

6P

Mass Flow

I

in.

6P

\Mass Flow

No.

in.

of water,

Ib/min

in.

of water

Ib/min

of '"ater

Ib/min

20 -0.227

ＭＲＱｾ

-0.045

-190

19 -0.200

-201

-0.044

-188

0.0012

24

18 -0.176

-188

-0.041

-181

0.0030

37

17 -0.152

-175

-0.036

-172

0.0042

44

16 -0.129

-161

-0.031

-160

0.0049

47

15 -0.106

-146

-0.026

-146

0.0053

49

14 -0.083

-130

-0.021

-129

0.0055

50

13 -0.061

-111

-0.015

-110

0.0055

50

12 -0.039

-88

-0.009

-88

0.0056

50

11 -0.016

-57

-0.004

-56

0.0056

51

10

0.006 ₃₇

0.002

39 0.0058

51

9

0.028

80

0.008

81 0.0062

53

8

0.049

108

0.014

108 0.0063

53

7

0.072

129

0.021

129 0.0063

53

6

0.093

148

0.027

147 0.0062

53

5

0.115

164

0.033

163 0.0060

52

4 .

0.137

179

0.038

176 0.0056

50

3

0.161

194

0.043

187 0.0049

47

2

0.185

208

0.047

194 0.0035

40

1

0.212

223

0.048

197 0.0014

25 NOTE -

Outside Wall

Vertical Shaft

Floor

+

flow into bUilding

-

flow out of building

+

flow into shaft

-

flow out of shaft

+

upward flow

-

downward flow

Total Infiltration Rate

into building -

1470 Ib/min

into shaft

-

1421 Ib/min

From: "Computer analysis of smoke movement in tall buildings"

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9 4 3

5

7

6

2 8 1 15 13 14

I - - t - '

_J

I

Ｈｾ

20

Note: Arrows are ot to scale

l-t}--..

FroIn: IICoInputer analysis of sInoke InoveInent in tall buildingsl l _by

G.T. TaInura, DBR/NRC, March 1969