# Ventilating a space with one inlet/outlet **URL:** \ **Category:** Factual Questions\ **Created:** [March 22, 2013, 11:47pm UTC](https://boards.straightdope.com/t/ventilating-a-space-with-one-inlet-outlet/653694 "2013-03-22T23:47:06Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![11811](https://avatars.discourse-cdn.com/v4/letter/1/9d8465/32.png) [@11811](https://boards.straightdope.com/u/11811)\ **Post date:** [March 22, 2013, 11:47pm UTC](https://boards.straightdope.com/t/ventilating-a-space-with-one-inlet-outlet/653694/1 "2013-03-22T23:47:06Z")
You have a room with one door and no windows. Could you better ventilate the room with a fan by blowing air into the room or by blowing air out of the room? ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 23, 2013, 12:04am UTC](https://boards.straightdope.com/t/ventilating-a-space-with-one-inlet-outlet/653694/2 "2013-03-23T00:04:26Z")
ventilation works better sucking air. ---
**Author:** ![SCAdian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/scadian/32/3292_2.png) [@SCAdian](https://boards.straightdope.com/u/SCAdian)\ **Post date:** [March 23, 2013, 12:30am UTC](https://boards.straightdope.com/t/ventilating-a-space-with-one-inlet-outlet/653694/3 "2013-03-23T00:30:56Z")
Sucking air into the room, or sucking air out of the room? ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 23, 2013, 12:33am UTC](https://boards.straightdope.com/t/ventilating-a-space-with-one-inlet-outlet/653694/4 "2013-03-23T00:33:07Z")
suck air into the larger space, so out of the room. ---
**Author:** ![11811](https://avatars.discourse-cdn.com/v4/letter/1/9d8465/32.png) [@11811](https://boards.straightdope.com/u/11811)\ **Post date:** [March 23, 2013, 1:48am UTC](https://boards.straightdope.com/t/ventilating-a-space-with-one-inlet-outlet/653694/5 "2013-03-23T01:48:56Z")
That is not the answer I expected. Is this a well-known fact? ---
**Author:** ![TurboNuke](https://avatars.discourse-cdn.com/v4/letter/t/f19dbf/32.png) [@TurboNuke](https://boards.straightdope.com/u/TurboNuke)\ **Post date:** [March 23, 2013, 1:57am UTC](https://boards.straightdope.com/t/ventilating-a-space-with-one-inlet-outlet/653694/6 "2013-03-23T01:57:01Z")
At work, to ventilate confined spaces we blow in. ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [March 23, 2013, 2:11am UTC](https://boards.straightdope.com/t/ventilating-a-space-with-one-inlet-outlet/653694/7 "2013-03-23T02:11:21Z")
What is the plan, to put the fan in the open doorway? Either way will move roughly the same amount of air, but place the fan to blow into the room to achieve better air mixing. The reason for this is that the air leaving the fan has a higher velocity than the air entering the fan. Stand a few feet in front of a fan and then a few feet behind a fan and you’ll be able to understand the difference. If you have it blow out you won’t have much air movement in most of the room. This assumse that there is free space in the doorway to allow air to leave the room. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [March 23, 2013, 3:06am UTC](https://boards.straightdope.com/t/ventilating-a-space-with-one-inlet-outlet/653694/8 "2013-03-23T03:06:38Z")
Hot air rises, so if the room is too warm, another reason to blow air into the room (assuming the fan is on the floor in the doorway) is that it will be blowing in cooler air, and pulling out the warm air closer to the ceiling. ---
**Author:** ![11811](https://avatars.discourse-cdn.com/v4/letter/1/9d8465/32.png) [@11811](https://boards.straightdope.com/u/11811)\ **Post date:** [March 23, 2013, 4:55pm UTC](https://boards.straightdope.com/t/ventilating-a-space-with-one-inlet-outlet/653694/9 "2013-03-23T16:55:02Z")
This question was prompted by me experience in an apartment I no longer rent. I would not open the window during the winter months, but had a small (12 inch) fan pointing into the bathroom to help ventilate. I assumed fan blowing into the room would be more efficient but I didn’t know why. Dag Otto, your explanation seems sensible.