Green’s Dictionary of Slang

huffer n.2

[huff v. (2)]

(drugs) an inhalant abuser.

[US]Current Sl. III:3.
[US]E. Richards Cocaine True 114: Hustlers inside the abandoned buildings sold [...] Taiwal for two dollars to the ‘huffers’ who wanted a quick breathy high.
[US]ONDCP Street Terms 12: Huffer — Inhalant abuser.