To add to the ammonia flammability discussion. Ammonia has a unique history in terms of classification. There has always been disagreement on the LC50 and flammable values of Ammonia. The US used a study that indicates a LC50 value of 7,338 ppm while the rest of the world used a value of 4,500 ppm. Since the LC50 is greater than 5000 ppm, the US transportation regulations classify it as a Nonflammable Gas (2.2) with the added requirement of Inhalation Hazard (The only non flammable gas to have this) The rest of the world classified it as a Toxic Gas (2.3) because the LC50 was <5000 ppm. Transport Canada however during the implementation of HM-181 created a new classification Corrosive Gas (2.4) in the early 1990’s. This has since been abandoned. During the updates in 2008 to ISO 10298, I was able to get the US and  European toxicologists agree that the most relevant study was the 7,338 ppm however the ADR, IMO and IATA  will still classify it as a toxic gas due to history. So if you ship Ammonia internationally it must have the hazard classifications on the cylinder for the receiving country while the container is marked with the US classification and is changed at the port. If your facility is in a port district the container can be marked for the receiving country if it is not transported outside the port district

Since most ammonia is used for agricultural use, the key standard is ANSI K-61.1/CGA G-2.1 “American National Standard Safety Requirements for the Storage and Handling of Anhydrous Ammonia”. I chaired the revision of this standard in 2006, most of the participants were agricultural and fertilizer associations from the mid-west.

Farmers can tow a 1,000 gal nurse tank properly placarded as a non flammable gas inhalation hazard using their tractor from their supplier to the farm on local roads. They cannot exceed 25 mph. Since they are not driving interstate the DOT requirements do not apply other wise the requirement for the driver to have a CDL with a Hazardous Materials endorsement would apply since it is over a 1,000 lbs. The state gives them this exemption. It was reported in committee that there are over 200,000 nurse tanks in the US!

Eugene Ngai

Chemically Speaking LLC

www.chemicallyspeakingllc.com