9-5。2 Heating and Air Conditioning。  See paragraph 2-4。5。  Most new paint spray booth ventilation systems have a painting mode and a curing mode。 Do not re- circulate air during the painting mode。 About 10 percent of the booth airflow is from outside the booth and 90 percent of the exhaust air is recycled during curing。 Review the paint drying requirements before specifying temperature and humidity ranges。

Refer to ANSI Z9。7 for exhaust air re-circulation requirements。

9-6 SYSTEM CONTROLS。 Design system controls in accordance with paragraph 2-5。

9-7 RESPIRATORY PROTECTION。  See paragraph 2-7。3。

CHAPTER 10

AIRCRAFT CORROSION CONTROL HANGARS

10-1 FUNCTION。 Aircraft corrosion control hangars provide space and equipment for the corrosion control processing of aircraft。 Processes include: deicing, limited detergent washing and rinsing, paint stripping, corrosion removal, protective coating application and painting, and finish curing and drying。

10-2 OPERATIONAL CONSIDERATIONS。 See paragraph 9-2 for spray paint operation considerations。

10-3 DESIGN CRITERIA。 Design hangars in accordance with MIL-HDBK- 1028/1, Aircraft Maintenance Facilities and the specific ventilation system design requirements in this Chapter。

10-3。1 Exhaust Air System。  The ventilation system for an aircraft corrosion control hangar is mainly to prevent fire and explosion。  A well-designed ventilation system will also reduce paint overspray, help control workers’ contaminant exposure, and protect the paint finish。 Workers must use appropriate respiratory protection irrespective of the airflow rate。 On 8 April 1997 and 1 July 1999, OSHA issued interpretations of 29 CFR 1910。94 and 1910。107 for determining the airflow rate required for an aircraft corrosion control hangars。 In accordance with OSHA’s interpretation letters, see Appendix D, an aircraft corrosion control hangar must minimally comply with the requirements of NFPA 33 and with Subpart Z of 29 CFR 1910 for hazardous substances。

NOTE U。 S。 Army: Army facilities will be designed to the requirements of 29 CFR 1910。94 and 1910。106 as well as NFPA33 and Subpart Z of 29 CFR 1910。

10-3。1。1 Painting Mode。  Design the volumetric airflow rate to keep the concentration of vapors and mists in the exhaust stream of the ventilation system below the 25 percent of the LEL。 See 29CFR1910。94(c)(6)(ii) for an example of airflow rate requirement calculations。  However, this calculated airflow rate often is too low to capture the paint overspray。 Do not re-circulate exhaust air while painting。

NOTE U。 S。 Army and U。S Air Force:  Recirculation of exhaust air may be considered provided requirements of ANSI Z9。7, NFPA 33, ASHRAE, and OSHA are met。

10-3。1。2 Drying Mode。 Review the paint drying requirements before specifying temperature and humidity ranges。 Consider maintaining the airflow rate at the same level as in the painting mode for the simplicity of the system。 However, a lower ventilation airflow rate can be used for the drying mode to conserve energy。

Recirculation of exhaust air can be used if sufficient outside air is provided to keep the concentration of vapors and mists in the exhaust stream of the ventilation system below

the 25 percent of the LEL。 Note that the quantity of off gassed vapors is higher early in the drying process, tapering off at the end of the drying cycle。 Refer to ANSI Z9。7 for exhaust air re-circulation requirement。