off-gas
1 of 2noun
ˈȯf-ˌgas 
plural off-gases also off-gasses
: a gas that is produced as a by-product of an industrial process or that is given off by a manufactured object or material
Refinery off-gases from fluid catalytic cracking could be a source of ethylene. 
Predicasts Technology Update
Predicasts Technology Updateoff-gas
2 of 2verb
off-gassed; off-gassing
transitive + intransitive
: to give off a typically harmful gas
In addition, OSHA intends to amend the hazard communication provisions of the standard to require hazard warning labels for solid materials capable of off-gassing formaldehyde at levels between 0.1 ppm and 0.5 ppm … Chemical & Engineering News
Chemical & Engineering News… there have been environmental concerns about the phenol formaldehyde binders used in most engineered-wood products, which can off-gas. Max Alexander
Max Alexander
Word History
First Known Use
Noun
1955, in the meaning defined above
Verb
1974, in the meaning defined above