Can cylinders of Anhydrous Ammonia (NH3) be stored with oxygen cylinders? This is not meant to be a trick question, but it is a question I find to be confusing for employees who place cylinders into storage. So what is your answer:
Can cylinders of Anhydrous Ammonia (NH3) be stored with oxygen cylinders?
As we can see, the label on compressed gas cylinders is a DOT label and for the life of me, I am not sure why these cylinders do not have to be labeled per 1910.1200(f)(1) Labels on shipped containers. All other shipped containers these days have GHS labels, but even if an NH3 cylinder was shipped with a GHS compliant label the user would still be challenged as to where the cylinder can be stored. Here are the GHS label elements for NH3:
Did you notice that none of the pictograms are for flammable gas, but yet it is listed as a Flammable Gas? Members can see my 2018 post – Anhydrous Ammonia is a flammable gas (OSHA) but shipped as a toxic gas
So how would an employee know that this Category 2 Flammable Gas must be stored with other flammable gas cylinders and not with oxidizers?
We know of the requirement:
1910.253(b)(4)(iii) Oxygen cylinders in storage shall be separated from fuel-gas cylinders or combustible materials (especially oil or grease), a minimum distance of 20 feet (6.1 m) or by a noncombustible barrier at least 5 feet (1.5 m) high having a fire-resistance rating of at least one-half hour.
Although NH3 is not a welding gas, we have seen OSHA use this requirement for all types of flammables and oxidizers. Pay special attention to the wording “fuel-gas cylinders or combustible materials”. It is my professional opinion that a Category 2 Flammable Gas can not be stored with Oxidizers/Oxygen cylinders, even though it is NOT labeled as a flammable gas.
As we can see from 1910.1200 App C there are no pictograms(s) for a Cat 2 Flammable Gas
