What does that mean? IMC 403.2.1(3)

[rktect 1]

Seriously, what does this mean? It states recirculation is prohibited. Next sentence it is not prohibited. The third sentence, it is prohibited again.

 

[classicT]

Is this the language you are referring to? "Where mechanical exhaust is required by Note b in Table 403.3.1.1, recirculation of air from such spaces shall be prohibited. Recirculation of air that is contained completely within such spaces shall not be prohibited. Where recirculation of air is prohibited, all air supplied to such spaces shall be exhausted, including any air in excess of that required by Table 403.3.1.1."

Note b. "Mechanical exhaust required and the recirculation of air from such spaces is prohibited. Recirculation of air that is contained completely within such spaces shall not be prohibited (see Section 403.2.1, Item 3)."

Ok, doing my best to convert this over to plain language using a smoking lounge as an example. A smoking lounge requires mechanical exhaust per Note b in Table 403.3.1.1. It is not permissible, per the first sentence of 403.2.1(3) to recirculate this air to other parts of the building. The second sentence does allow for the recirculation of the air if that air (presumably contaminated) is completely contained to that space (i.e. a dedicated HVAC unit).

2015 IMC Commentary is pictured below...

 

[rktect 1]

I was looking at a dog grooming business. Same exact notes and code section. So as long as the dog grooming business, which is like 1200 sq. ft. in area, has its own HVAC system, it can recirc that air all day long?

 

[classicT]

Still needs the minimum ventilation air, so a portion will need to be exhausted and fresh air brought in.

 

[steveray]

I think it is saying you can't recirculate the air that is to be exhausted, but you do not have to exhaust all of the "return" air....Simplest I can think of...

 

[Sifu]

I have always taken it that it can be recirculated if it is the same air you are sucking up and then just moving it to another portion of the same environment.