We know that ammonia has a pungent odor, however, you can not just base a fan on odors only unless they are considered nuisance to the workers. You should size a fan based on the acceptable breathing level known as the threshold limit values (TLV) published by the American Conference of Governmental Industrial Hygienists (ACGIH) if persons entering the ammonia storage and equipment room to perform tasks. To size the fan CFM, You'll need to estimate the maximum concentration, the TLV, time to evacuate the vapor under steady state conditions and room volume. Nonetheless SCUBA respirators will be required for any emergency repair. In engineering rooms ( not talking about engine rooms) where engineers do their work and make copies of their blue prints with ammonia copying machines, a local exhaust fan will be needed since the ammonia vapor emitted from the blue prints will be overwhelming but not necessarily exceeding the TLV short term exposure limit (TLV-STEEL) limit from ACGIH. In addition Ammonia vapors are considered flammable, however, since its lower flammable limit has a concentration level much greater than ACGHI TLV,the onset of fire is substantially minimized unless you have impingement of vapor on spark producing equipment. One last thing is that the odor thresholds of contaminants are much lower than their threshold limit values, therefore, realize that awif of ammonia does not necessarily mean that a respiratory or fir fire hazard exist.
" Do we need inlet fan?" use exhaust fan otherwise inlet fan will distribute the vapor throughout the building.
