1) Not respirable 2) Unfit for breathing 
• (a.) Unfit for respiration; not having the qualities necessary to support animal life; as, irrespirable air.
1. Incapable of being inhaled because of irritation to the airway, resulting in breath-holding. ... 2. Denoting a gas or vapor either poisonous or containing insufficient oxygen. ... 3. Denoting an aerosol composed of particles with aerodynamic size larger than 10 u. ... (05 Mar 2000) ... 
Ir·res'pi·ra·ble adjective [ Latin irrespirabilis : confer French irrespirable . See Respirable .] Unfit for respiration; not having the qualities necessary to support animal life; as, irrespirable air. 
Type: Term Pronunciation: ir′re-spīr′ă-bĕl Definitions: 1. Incapable of being inhaled because of irritation to the airway, resulting in breath-holding. 2. Denoting a gas or vapor either poisonous or containing insufficient oxygen. 3. Denoting an aerosol composed of particles with aerodynamic size larger than 10 μ. .....
not respirable; unfit for breathing.