3003 W CASINO RD BLDG 45-01 2018-01-01 MF Import

August 18, 19?5 4-3212-4-389 To: K. Carlson OF-49 cc: L. VanTassel OF-10 K. Hayes OM-31 W. Henkel OF-49 Sub�ect: Building 45-01 , Everett Ventilation for Hazardous Locations Reference: (a) 5ummary of lower explosive limit (LEL) calculations prepared for the subject hangar in response to the concerns of flammable vapors present during painting and paint curing (recirculation mode) of aircraft (b) Everett SHEA Report No. 4-1221-9000-252, April 6, ]990, regarding study of employee exposure to chemicals in the basement of the Buildin9 45-01 paint hangar Fire Protection Engineering has reviFwed the reference (a) calculation suiamary for the ventilation during painting and curing of aircraft in the sutject hangar. This is being reviewed as part of the overall paint hangar renovation project currently under design by Austin. The new design will inciude a heated cure cycle with air rec�rculation following a paint job. One concern is the possibility of reaching an LCL level in the supply/recirculation plenum located at the top of the hi9h bay followin9 a paint job. LEL calculations were done and based upon the safety ventilation � _ � methad for Class A ovens given NFPA 86, "Standard for Ovens and Furnaces", 1990 edition. These calculations indicate that �if3`gallons of paint thinned � with 50X MEK solvent would be needed to reach an LEL level of 25% in a cure cycle with 330,000 cfm of recirculation and 110,000 cfm of exhaust/make-up (exhaust at 120'F) . This is at least 10 times the amou�t of paint mixed (not necessarily used) duri�9 the painting of an all white 741 aircraft (wurst case) . This indicates that the proposed ventilation rates would be more than adequate to keep vapors at below the LEL range in the supply plenum during cure. This is also in support of keeping electrical equipment including the supply fan motors in the plenum rated for ordinary electric rather than Class I. It is also part of the paint specificatians to run the ventilation in the paint mode (100X exhaust, no recirculation) for at least one hour following painting rather than going straight from a paint mode to a cure cycle. This would further reduce the amount of volatiles flashing off once cure starts. The other scenario is far a dump of solvent (toluene or MEK) during priming. The downdraft ventilation system will be in a 100� exhaust mode durin9 fullynexhaustedWfor• thendurat�on ofmpriminge(andPpainting� asewell�dingtand would take a dump of 29 gallons of MEK to reach a 259. LEL level in the basement with no ventilation going at all . This is based on a basement volume af 300,000 cfm. It would take a dump of over 2600 gallons of MEK with the ventilation gaing to reach a 25Ye LEL level in the basement.