# Repair Garage Ventilation



## Mech (Mar 10, 2010)

2009 IMC / IBC

Table 403.3, footnote b - Mechanical exhaust required and the recirculation of air from such spaces is prohibited.

So is this saying mechanical ventilation is required and natural ventilation is no longer acceptable?


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## Dr. J (Mar 10, 2010)

Re: Repair Garage Ventilation

No.


"_401.2 Ventilation required._
_Every occupied space shall be ventilated by natural means in accordance with Section 402 or by mechanical means in accordance with Section 403._"
You go to table 403.3 only if you choose not to do Section 402 natural ventilation.

The bigger question is, can a natural ventilation system be made code compliant?  If by "natural ventilation" you mean just open the garage door, then the answer is "maybe, maybe not".  How will such an arrangement meet both IMC 401.3 "_Ventilation shall be provided during the periods that the room or space is occupied._" and IBC 1204.1 "_Interior spaces intended for human occupancy shall be provided with active or passive space-heating systems capable of maintaining a minimum indoor temperature of 68°F (20°C) at a point 3 feet (914 mm) above the floor on the design heating day._

_Exception: Interior spaces where the primary purpose is not associated with human comfort._"?

Perhaps an argument can be made that the primary purpose is to keep the shop floor dry, and the it is no worse than having the occupants just suck it up and do this work under a wall-less canopy.

BTW, this set of code sections makes "just open the window" natural ventilation arrangements illegal in all of the U.S. for any type of office/apartment/retail kind of occupancy (where human comfort is a primary purpose).


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## Mech (Mar 10, 2010)

Re: Repair Garage Ventilation

The building code removes any ambiguity.

_IBC 406.6.3 Ventilation. Repair garages shall be mechanically ventilated in accordance with the International Mechanical Code. The ventilation system shall be controlled at the entrance to the garage._


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## klarenbeek (Mar 10, 2010)

Re: Repair Garage Ventilation

IMC section 502.14 also requires mechanical ventilation. Also I see the note "mechanical exhaust required" on table 403.3 as meaning just that--ventilation has to be by mechanical means, not natural. If natural ventilation were allowed in these occupancies, why the footnote saying mechanical exhaust required? Mechanical ventilation is required in ALL occupancies if natural ventilation is not used, so why bother making a note requiring mechanical exhaust if it really isn't required?

With regard to natural ventilation not being allowed in any occupancy such as offices or apartments, 402.1 requires the operating mechanisms to be readily available to occupants, leading me to believe that with natural ventilation it is up to the occupants whether or not they want the windows open.  Ventilation is provided for the occupants in accordance with 401.3, they just choose not to use it.  At least that's my humble opinion.


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## Dr. J (Mar 10, 2010)

Re: Repair Garage Ventilation

Mech - I concur and change my answer.  Mechanical ventilation required, one does not get to choose between IMC 402 or 403.

Klarenbleek - the exception to IMC 502.14 "_This section shall not apply to motor vehicle service areas where engines are operated inside the building only for the duration necessary to move the motor vehicles in and out of the building._" would exempt many repair garages (depends on services performed), but Mech's IBC reference still trumps the IMC.



> If natural ventilation were allowed in these occupancies, why the footnote saying mechanical exhaust required?


Because, unless trumped as in IBC 406.6.3  or any of the other sections specifically requiring mechanical ventilation, one gets to choose between either IMC 402 or 403.  If you have chosen IMC 402, you do not need to even look at IMC 403 (again, unless specifically directed there by another section).

The OP has been  answered, so rather than getting off track on natural ventilation of other spaces I "take this outside" to a new thread.


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## EPrice (Mar 22, 2010)

Re: Repair Garage Ventilation

While we're talking about it, take a look at NEC (2008) 511.3©(1)(a)  Compliance with that subsection is not mandatory, but since they are required to have mechanical ventilation any way, they may as well comply and get the benefit of not needing to classify the floor area.


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## gvictor (Mar 22, 2010)

Re: Repair Garage Ventilation

For repair garages go to Section 2211 to find additional ventilation requirements.  Since we must deal with both heavier and lighter than air fuel vapors, it is becoming more difficult to deal with these days.

Greg


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