War Construction Gives lmpetus to Fireprooled \(/ood

Bv P. R.

The pressure impregnation ttf wood rvitlt lire-resistant chemicals is not new in the United States. lSefore the turn of the century the United States Navy specified lireproofed r,r'ood for a uttmber of purposes, and the navies of several European cottntries have usecl fireproofed rvoocl for over 4O vears. Fireproofed n'ood is not to be colrsidered as a neri material developed b1' An'rerican genius nncler thc stress of n.ar. I)uring almost a half centtlry of commercial use in this c()tlntry a l'ealth of information anil fttnclamental data basecl upon contirtuing research madc it possible to suppll' fire-retardant ltttnller ttl the Arml', Navr' arrcl other Governtrtent cleparturents as u'ell as to \\-ar and other plants for a nrultitude of outst;rntling irrstallations' When alternate lrrriltling material lrcczrtne "critical" bc-

Hicks*

to believe that successful lireproofing treatment u'ill sirnilarly be an invaluable aid to the lurnber industry in the immediate future rvhen priorities rvill be a thing of the past, and the present so-called "critical" materials rt'ill return more vigorouslv tharr ever into full competition with rvood in many fielcls. 'fhe availabilitv of hre-retardant rvoocl should aid materiallv also in retaining the new r.narkets for u'ood createcl dttring the rv:tr by scarcity of other construction materials, and in ltreventirrg a rectlrrence of conclitions existing in pre-u'ar clavs. u'hen a declin-

The timber in these huge blimp hangats, opproximctely 300 x 1,000 lt. in size, ond 170 feet inteishtir:Hft;:::re treqted lor protection cause of the exigencies of u'ar, the attcntittn of the engineering profession tu'rnecl to rvood. As a rct;ttlt approximately 75,000,000 ft.of fir-eproofed r'r'ood has lreen used during the past trvo years. It has been usecl u'ith equal satis{action in structures of huge dimension or irr relatively small structures ; and it has been used in fielcls of construction rvhere ll'ood had never before been given entree.

The lumber industry has long been familiar with the accomplishments of the u'ood-ltreserving industry and with the success obtained in protecting u,ood of all forms from destruction by decay, termites and marine borers. It is generally recognized that much of the construction into which the billions of feet of treated timber have been poured would otherwise have gone to some material more permanent than untreated u.ood. There is every reason ing rr-rarket {or rvoocl in general st.rtnctimes contrasted rather painfullr- u'ith-a consistent ancl consectttive yearly rise in the market for competing rnaterials.

*S"...a"."-Manager, Service Bureau, American'Wood-Preservers' Association, Chicago, Ill.

'I-he principal effects of fireproofing treatments are to retard the norrn:rl increase in temperzrtures under fire conditions, to clecrease the rate of flame spread and ignition of the rvood, to lessen the rate o{ flame penetration or destruction of wood in contact rvith fire, ind to extinguish fires more easily. No better description of fireproofed woocl and the manner in 'ivhich the treatment prevents ready ignition and spread of flame can be written than the follo'rving given by one of the leaders in the industry:

"Fireproofed wood is chemically impregnated wood rendered permanently incapable of supporting combustion. When heat is applied to fireproofed wood it begins to decompose the injected chemicals into non-poisot.tous gases which are not only noncombustible but rvhich serve to prevent the oxygen of the air from gaining access to the r.vood rvhich is being heated. Hence, combustion is in-

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BIdq. EXbrcoL ?(Xl LO6 ANGEIIS STI.ES OFFICE fi10 Petrolcum Bldg. PnorPccl 615

SPECIES

PONDENOSA PINE (PINUS PONDEROSA)

SUGAR (Genuirre WLito) PII{E (PINUS LAMBERTTANA)

WtrJ\4INGTON 1446 Ecrst Ancrheim SL Wilnr. 0120-NE" 6-1881

(Continued from Page 16) hibited. As the application of heat continues a series of endothermic reactions takes place. Checking, charring and slow destruction continue without contributing any fuel value; i.e., no increment in temperature occurs. The surface of the wood manifests only a slight glow, and that portion of the rvood bordering on the surface that is directly exposed to the flame, depending upon its intensity, likewise checks and chars. The gradual distintegration of the wood results by virtue of dry distillation without bursting into flame or spreading blaze. The wood is reduced to a clinker-like charred condition and not to an ordinary ash. Effective fireproofing compounds increase the yield of charcoal by slow dehydration of the wood substance."

The treatment of .wood for fire retardance differs little in detail from the vacuum pressure treatment with salts for protection against decav and insects. The usual meth- other public buildings for such purposes as flooring, inside window frames anil sash, doors, trim, and other interior finish unless fireproofed to meet certain required tests. These tests, commonly called the shavings, crib, and timber tests, are still used to some extent. Briefly, the shavings test was one in which flame from a gas burner was applied to a quantity of fireproofed shavings, which to pass the test successfully must not show any flame or glow after a certain number of seconds following rembval of the ,burner. The timber and crib tests .were applied to samples of wood subjected to certain flames for a period of time, after which the unburned area and .loss in weight were tabulated. The tests most commonly used todav are the Krefeld test as provided in the Ameiican Society for Testing Materials specifications C16O-41T and the test commonly referred to as the fire tube test suggested by the Forest Products Laboratory at lVladison. Wisconsin. Irr

All the cross-wdlks, rcils, plctlorms, etc., in this syathetic rubber plcnt preasute trected wiih lire-retardqnt gcrlte, od of fireproofing rvood is to place the lumber on specially built steel tram cars, which are ruu into the steel treating cylinders (from @ to 180 ft. long and 5 to9 ft. in diameter), bolt the door, and force the chemical solution into the wood under pressure of 100 b 2AA lbs. per square inch. A vacuum of approximately ZZ in. is usually applied first when dry lumber is to be impregnated, ltut if the wood is green it is first conditioned by steaming for a short period of time at not over 20 lbs. gauge pressure of. 2590 Fahrenheit before the vacuum is applied. The time of treatment depends upon the species of wood, its size and moisture condition, and ma/ require a pressure period of 24 hours or more before the necessary absorption is obtained, although the tirne may vary somewhat with the temperatures and pressure used.

Unlike in the wood-preserving industry, where laboratory tests have not been accepted as reliable evidence of the value of a preservative material, such tests are of prime value and reliability in determining the'success of any given fire-retardant treatment. Fire follows a very definite pattern in every case, and on the authority of the American Society for Testing Materials a standard timetemperature curve has been plotted which best illustrates conditions in the averdge fire. These conditions can be duplicated in a laboratory, and the fire resistance of the product thus measured.

Interest in fireproofed wood in early days was most marked in New York City, which saw great possibilities in its use in building construction, and about 40 years ago the building code of that city prohibited the use of wood in any buildings exceeding 150 ft. in height or in .certain qre wood,

Hcngcr during constuction with some of the treqted timber arches in plcce. these tests small samples of the fire resistant wood are elposed to flame at a temperature exceeding 18000 F. and the suitability of the treated lumber is mJasured by the loss in weight resulting from such exposure.

The economical aspect of fireproofed wood should eventually, of course, be reflected in premium reductions by fire insurance groups. The undenvriters will acceDt fireproofed lumber for structural uses. Various national technical associations-among them the American Wood-Preservers' Association, the American Society for Testine Materials, and the American Railway Engineering As"sociation-have taken sufficient interest in the-probleri to undertake the writing of detailed specifications governing the treatment of the material. These may not be completed for some time, but it is interesting to note that wo;k already done lry ttr" committees studying the subject indicates an active and growing interest in fireprooied wood by constructing agenJies.

The widely publicized blimp hangars designed by the Navy and erected at various points throughouit the Atlantic, Gulf and Pacific coasts constitute the largest use for commercially fireproofed lumber in this coun-try. These vast 'preframed wood structures made possible by the use of Teco connectors are protected agalnst both- fire and decay by treatment. The fireproofed-wood used for these Navy blimp_ hangars was specified by the Navy to be treated in accordance with the American Wood-Preservers, Association specifications No. 38b for the treatment of lumber by the pressure processes. In brief, the specifications of (Continued on Page 21)

While most oI our lumber is going into Government wqr uses, we have been tcking ccre oI our deqler customers' requirements to the best ol our cbility, cnrd we thank them for their pctience curd coopercrtion

(Continued from Page 18) the Navy provide thdt the lumber shall not be de-graded by the impregnation process and the strength of thJstructural wood shall not bq impaired by tEe chemicals or processes. The treatr.nent shall be permanent under normal exposure conditions, and the chemicals shall not corrode metals, affect paint or glue, create hazards of health (uring the handling or working of the material, or emit injuriou_s fumes under direct fire attacks. The fireproofed material must pass the American Society for Testing Materials test for fire-retardant properties -of wood, referred to above as the Krefeld test.

Tests made by various testing laboratories on fireproofed 'wood that has been in service -for many years in the New York area have found it to be as fire resistant as when installed. With increased production of this material, there has bee! a general reduction in its cost over a period of years, so that'at present the cost of treatment.dois not exceed that of a good ireosote treatment, and the wood is not only made fire resistant but decay and insect resistant also. , There are now twenty odd pressure plants in_1!ris country in position to furnish this product. ^ . While fir_eproofed wqod has been a. realily for years, it ' has generally been used for less colorful 'purpoies than the construction of blimp hangars to aid in the prosecution of a conflict which has weakened destruction on a great p,art of the civilized world. It may well be, however,-that the impetu.s. given this product ihrough its use by the Navy for this purpose and by other Government d6part- ments for various defense structures will serve to focui the attention of lumbermen, architects, engineers and builders 'on a development which bids fair to effect as great possi- bilities for lumber and timber producers as did the development of the wood-preserving industry. The more common uses for fireproofed material are framing, lining and roof decking for railroad roundhouses and shops, store buildings, wharf superstructure buildings, garages, ships, schools, hospitals, residences, libraries and other public building,'scaffolding, etc. It is in such miscellaneous fields and many others yet untried that fireproofing will find its greatest application in the post-war era.

Use oI Certcin Grcrdes ol Lumber Restricted i' To Wcrr Work by WPB

Los Angeles, Calif., July 19.-Moving to channel several kinds of lumber into making of. boxes for militarv overseas shipment, the War Production Board today issued an order prohibiting use in 26 types of products.

More than half of this year's lumber production must go into -the crating and protection of ammunition, food, and other supplies for invasion for-ces, Stanley Mark, WPB priorities chief here, explained.

He said the "freeze" applied to specified grades of white oak, Idaho white pine, spruce, Ponderosa pine, sugar pine, white fir, and red cypress.

Norte of the types affected may be used inalist of products which includes agricultural equipment, boats, fixtures, flooring, furniture, mobile and pre-fabricated housing, refrigerators, toys, trunks, and lockers, Mr. Mark explained.

All lumber comes under drastic new controls on August 1 as result ofa critical shortage of materials for overseas military purposes.