Aerostatic Engineering — Hazardous Materials Safety Interpretation

Page 1J.S. Department of Transportation 400 Seventh St., S.W. Washington, D.C. 20590 Research and special Programs Administratior APR 24 2002 Mr. John Terry Reference No. 00-0117 Acrostatic Engineering 495 East Brokaw Road San Jose, CA 95112 Dear Mr. Terry: This is in response to your letter concerning the purging of a propane cylinder that will be offered for transportation by aircraft under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). You enclosed materials on outline your procedures for purging cylinder to a point where the fuel to air ratio is below 2 percent. You inquired how far under 2 percent is . purging required. We apologize for the delay. in responding and regret any inconvenience it may have caused. As you state, § 173.29(b)(2)(ii) requires that a cylinder be sufficiently cleaned of residue and purged of vapor to remove any potential hazard to be considered as not regulated under the HIMR. The methods and limits used for determining what qualifies as a "cleaned and purged" under the HMR are intentionally not defined because they vary greatly depending on the properties of the particular hazardous material and type of packaging. In the case of propane, other variables such as purge medium, temperature conditions and cylinder volume are also factors. We would consider a propane cylinder to be sufficiently cleaned and purged when the vapors in the cylinder are no longer capable of sustaining combustion. Of course, when a cleaned and purged cylinder is offered for transportation by aircraft, the cylinder valve must be left open to preclude internal pressure buildup, as prescribed in packing instruction 200 of the International Civil Aviation Organization's Technical Instructions for the Safe Transport of Dangerous Goods by Air. I hope this satisfies your request. Sincerely, Hothe 2. mith el Hattie L. Mitchell, Chief Regulatory Review and Reinvention Office of Hazardous Materials Standards • 173,29 000117#

Page 2FROM : PHONE NO. : 408 8676390 May. 07 2002 02:37PM P2 U.S. Department of Transportation Research and Special Programs Administration Office of Hazardous Material Standards DHM-10 Washington DC. 20590 400 7th. St. SW Dear Mr. Edward Mazzuilo I operate an FAA certified hot air balloon repair station (T4YR452N) in San Jose, California. A: shipment. ane of the services provided by the repair station, I prepare hot air balloon systems for ai I have had a number of customers comment on trouble they have had with recent air shipments. and ICAO rules require the tanks be empty and purged with the service valves open. Hot air balloons have propane fuel tanks, usually four tanks of 10 to 18 gallon capacity. FAA NO ONE HAS BEEN ABLE TO TELL ME HOW FAR UNDER 2% I NEED TO PURGE FOR AIR SHIPMENT. I have conducted a number of tests with various purging methods and variou percent fuel/air ratio. (Data attached) urging gases. The resultant data defines how much purging is required to reach a desires I have read your "Interpretation Letter" on tank purging and found it totally inadequate. There are no specific numbers for propane purging, therefore a person doing the purging has no idea if he has met the requirements. Could you please provide a more definitive "Interpretation Letter" that defines a "safe" purged Thank you for your help in this matter. Sincerely, Le Te Terr 495 E. Brokaw Rd. San Jose, CA 95112 Kathleen Roscher, Lead Special Agent#