Document 2RNg8zX21EG3d4ZRGK21ekpaL

as a mat for secure footing near wood-working or other machines involving senous danger to the operator if he slips and falls Lead is heat conductive, spark resistant, and quiet It should not be used for heavy trucking Zinc also is used for its spark-resistant qualities, but, compared to lead, it is attacked more readily by alkalies Floors in com pounding rooms where fire and explosion haz ards exist are zinc-covered in some plants Asphalt-base, vinyl-base or linoleum-type tile often is used in offices, laboratories, and workrooms where cleanliness and good looks are important The material is easily cleaned, noiseless, and a poor conductor of heat Magnesite is suitable for light traffic or where light oils are used It must be laid on a rigid base and should not be used where there is excessive moisture or hydrostatic pressure, as in basements A coating of bituminous paint is necessary to protect metals such as pipe from contact, since magnesite corrodes some metals Checkered steel plate wears well, but it is noisy and highly conductive of heat and elec tricity It is relatively nonshppery unless wom smooth or wet with oil Metal grille floors and gratings will not col lect dust, dirt, or liquids but, because of noise, are not often used where hand trucking is done regularly This type of floor material is particularly useful in boiler rooms and over openings Parquet is laid on an underfloor and is suit able for offices If the material is sealed prop erly, httle maintenance is necessary Parquet wears well but may be noisy Rubber flooring is resilient Italso has high dielectric strength, which is undesirable where static electricity is a problem How ever, conductive types of rubber flooring are available Abrasive rubber flooring can be used to overcome slippenness Since terrazzo flooring has no joints in the surface, its use eliminates some of the diffi culties that may be encountered with other types of flooring It can be made electrically conductive by grounded grilles It is a con ductor of heat Suitable sealers are necessary to make the floor impervious to most acids The terrazzo mixture is slippery unless it in cludes abrasive aggregates Plants requiring extreme cleanliness and sanitary conditions, such as dames, use ce ramic glazed tile It should be laid in Trin idad asphalt or in cement with a low lime con tent Two or three layers of asphalt roofing felt may be laid beneath the tile Wood floors of the proper material and con struction are suitable for various services ex cept for the obvious objection of a fire hazard Plank or board floors of the softer woods are generally unsatisfactory and a source of nu merous injuries from slipping and falling as well as from splinters and truck accidents A good floor for light manufacturing can be made From matched orjointed hardwood Boor ing nailed to a subfloor structure or to sleepers in concrete The thickness of the hardwood flooring will depend on the service to which it will be subjected It is laid with the grain parallel to the line of truck travel Wood blocks meet many of the require ments for a good floor Properly made, a floor of this type is relatively noiseless and does not become slippery or cause fatigue If the blocks are laid on a smooth, rigid base, the floor is not likely to crack and will withstand heavy service Blocks impregnated with creosote are nec essary for floors m contact with liquids or moisture Expansion joints are required along walls, columns, and similar places If blocks are laid with a high melting point pitch, hot weather does not create problems Oils and organic solvents, however, cause trouble because of their solvent effect on bi tuminous fillers and coatings To reduce tracking of mud and dirt into a building, moisture-absorbing mats or runners can be installed at entrances Special floonng Special types of floonng are necessary where fires or explosions may occur Sparkresistant and conductive floonng should be specified where flammable vapors, dusts, or gases are present Conductive floor resistance (as measured between two electrodes placed 3 ft apart at any points on the floor) may vary from not less than 25,000 ohms to not more than 1,000,000 ohms, according to NFPA's Flammable Anes thetics Code Standard No 56, to assure pro tection against electnc shock and still provide for removal of static These floors can be grounded at two or more points by means of copper strips stapled to the material or copper 415