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r. January-February, 1967 Isocyanates may be released when the The Ranta method which measures j polyurethane is subjected to heat. In the both TDI and TDI urea dependsion case of foam, excessive concentrations the yellow color formed when TDI is may be produced at temperatures above absorbed in an aqueous solution of 210017l0 2-ethoxyethanol (ethylene glycol TDI is frequently sold as a pre-polymer monoethyl ether), sodium nitrite and in which part or most of the isocyanate boric acid.' A recent improvement in is "blocked" by reaction with a polyol or the method has increased its sensitivity other active hydrogen-containing material. and made development of a field kit The pre-polymers or adduct resins can practical." vary widely in their monomeric (un- 2. Sampling and analysis of biological !— reacted) isocyanate content. The po- tential health hazard is in proportion to materials: No methods are available. the monomeric TDI content 30 Demonstration of antibodies in the serum may be indicative of recent ex- B. EVALUATION OF EXPOSURES: posure." 1. Air sampling and analysis: TDI reacts with water vapor to form TDI Urea. C. HAZARDS AND THEIR RECOMMENDED CON- It•reacts also with atmospheric phe- TROL: nols, cresols, alcohols and other active 1. Inhalation: Atmospheric iconcentra- hydrogen donors. The co-existence of tions of TDI should be.controlled by hydrogen donors with TDI may re- local and general exhaust ventilation duce rapidly the atmospheric con- to a point approaching zero. ' Where centration of TDI, the reduction being this is not practicable, as in foam a function of concentration and time. spraying or painting, adequate respira- It has not been established whether tory protection must be provided. Air the TDI urea has the same physio- line respirators, self-contained breath- logical action as the free TDI. In ing equipment or gas masks designed evaluating exposure to TDI, it is par. for protection against organic vapors titularly important that samples be and airborne particulates may be used. collected in the breathing zone be- All should have full face pieces. Dust". cause of the rapid disappearance of or paint respirators do not provide free TDI from the atmosphere. adequate protection." All respiratory The Marcali method depends on protective equipment should bear bubbling air through an acid collect. U. S. Bureau of Mines approval. ing medium, hydrolyzing the isocyan. Where feasible, a pre-polymer having ates to the amine, diazotizing and the lowest possible amount of free iso- coupling with N-1-naphthyl ethylene cyanate should be used. In foam diamine and measurement of the color spraying, the internal-mix gun pro- intensity at 550 millimicrons. With duces less atmospheric contamination permanent color standards, it is a than the external-mix." useful field method with a sensitivity Control should be provided where to 0.005 ppm. Greater accuracy and polyurethanes are heated to the point sensitivity may be obtained in the of decomposition, as in soldering laboratory by spectrophotometric de. polyurethane coated wire. termination. Aromatic amines inter. fere to give high values. Phenols and 2• Skin contact: All contact with liquid, cresols do not interfere with die vapor or mist containing TDI should method, although they may reduce the be avoided. Impervious clothing free TDI present in the atmosphere. should be provided when there is any The method does not react to TDI possibility of contact. urea.''-2' 3. Eye contact: Chemical workers gog.