# Ventilation - Intake Opening



## Mech (Oct 16, 2017)

2009 IMC

Are sections 401.4 and 401.5 (shown below) for mechanical ventilation only or does it govern natural ventilation in the form of doors and windows as well?  There is no definition for "Intake Opening" that I saw.  I am thinking this pertains to Mechanical Ventilation only, but then why is it under the General section and not under Section 403 Mechanical Ventilation?
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Section 401.4 Intake Opening Location.  Air intake openings shall comply with all of the following:
1. Intake openings shall be located a minimum of 10 feet from lot lines or building on the same lot.  Where openings front on a street or public way, the distance shall be measured to the centerline of the street or public way.
2. Mechanical and gravity outdoor air intake openings shall be located not less than 10 feet horizontally from any hazardous or noxious contaminant source, such as vents, street, alleys, parking lots and loading docks, except as specified in Item 3 or Section 501.2.1.
3. Intake openings shall be located not less than 3 feet below contaminant sources where such sources are located within 10 feet of the opening.
4. Intake openings on structures in flood hazard areas shall be at or above the design flood level.

Section 401.5 Intake opening protection.  Air intake openings that terminate outdoors shall be protected with corrosion-resistant screens, louvers or grilles.  Openings in louvers, grilles and screens shall be sized in accordance with Table 401.5, and shall be protected against local weather conditions.  Outdoor air intake openings located in exterior walls shall meet the provisions for exterior wall opening protective in accordance with the International Building Code._


IF Sections 401.4 & 401.5 include doors and windows for natural ventilation, then 401.5 says they are required to have screens, louvers or grilles meeting the opening sizes in Table 401.5.  For residential applications, the opening sizes can not be less than 1/4" or greater than 1/2".  Window screen openings are smaller than 1/4" and not all doors have screens, so doors and windows would not be allowed for natural ventilation.

IF Section 401.4 does NOT apply to natural ventilation, it is OK (per the IMC) to locate a door and window for natural ventilation within the minimum distances written in 401.4.  This just seems a little odd to me to allow the ventilation opening close to a contaminant source.


Thanks for setting my head straight.


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## north star (Oct 16, 2017)

*@ ~ @*

Mech,

As I understand Section 401.4 & 401.5, these Sections are intended
*for "required air"  [  i.e. - necessary  ] for the functional operation*
*of a system, such as a plumbing vent system, mechanical exhaust,*
*etc., whereas the doors & windows are for "optional air".*

*If a door or window is going to be located near a "required air"*
*opening, then Item # 2  &  Item # 3 above provides the dimensional*
*distances of separation "required" for those doors or windows*
*[  i.e. - min. of 10 ft. away horizontally and or \ 3 ft. below a*
*source of contaminants  ].*

*As I understand the "Openings in the Screens", the intent is to*
*protect the "required air" openings from being clogged \ closed*
*by stuff that could cause the "required air" systems to malfunction*
*and be unable to remove the contaminated air in the structure*
*from being removed to the exterior.*

*Screens on doors & windows in Residential applications is for*
*"optional ventilated air"........Also, I do not believe that screens*
*are "required" on Residential windows.*

*Does this help ?*

*& = &*


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## Francis Vineyard (Oct 17, 2017)

First in accordance with 401.2 "assumes that a building will be in full compliance with one method or the other. There are no provisions in the code for a ventilation system that depends simultaneously on both natural and mechanical ventilation."

The general provisions of 401.4 and 401.5 are applicable to both mechanical and (natural) gravity outdoor air. However note 401.5 is specific to air intake openings that "terminate" outside in harmony with exhaust openings that "terminate" outside in Sections 501.2.2, 504.4, kitchen exhaust, chimneys, etc.

I suppose were it not for mechanical ventilation then it would not be allowed to have doors and windows that are required for natural ventilation to be located within 10 ft. of lot lines, buildings on the same lot, etc.

Also reference to natural ventilation see IBC Sections 1203.1 (1203.4 and 1206) or IRC 303.1 (303.4 and 303.5).

FWIW Virginia amended the code where natural ventilation through windows and doors is required an insect screen shall be provided.


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## steveray (Oct 17, 2017)

I believe it applies to both....


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