positive or neutral pressure space? 1

[Ahmedbadr87]

Hello all,
Is there any reference or recommendation In Ashrae to maintain positive pressure or neutral pressure in different spaces.I know about Hospitals that most space should be kept under negative pressure But for other different occupancy like Office buildings, restaurants , stores...etc I'm not able to find.If there is not something like this in Ashrae what is the good practice for this matter?

Thanks in Advance

 

[urgross]

If it smells bad, keep it under negative pressure or offer a minty breath mint.

 

[Ahmedbadr87]

No, it doesn't smell bad.so in spaces where there is no smeel.Is it preferable to make the space neutral or positive pressure?

 

[Ajender]

But for other different occupancy like Office buildings, restaurants , stores...etc ... this is your question. Max hospital view all rooms have Negative pressure . Some other places depends on Place and Type of Rooms. But My answer is Positive.

Thanks

 

[GT-EGR]

ASHRAE 62.1 actually has a space type classification, which categorizes rooms as far as nuisance odors. It uses this to recommend what space air is allowable to transfer to another space and count as ventilation.

Generally speaking, you have to ask yourself which space you think has more odors/contaminants, and then that will dictate your pressurization strategy. ASHRAE 62.1 will help, but in the end if you can defend your airflow directions to a reasonable person I don't think you will get much resistance. And if you can't decide on a couple of space types, then it likely doesn't matter either way.

 

[itsmoked]

Hospitals are negative? Negative space screams external contamination to me.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ChasBean1]

GT-EGR is right. To add, there are some spaces with pressure requirements, e.g., USP 797 pharma manufacturing facilities might recommend a minimum ±0.02" w.c. depending on need for personnel protection or cleanliness of product. An OR is +0.02" minimum based on current FGI guidelines (U.S.). BSL-3 spaces might lean toward a -0.05" value, etc.

Typically a combo lab/office building benefits from a positive airflow from office to lab (no strict DP requirement). A building in general is good at neutral pressure to maybe +0.01". But no requirement on that front either.

 

[SAK9]

If in a tropical type humid weather such as in the Middle East, I would maintain the space mildly positive to keep the moisture out otherwise you diffusers might rain on you

 

[ChasBean1]

Too true SAK9! So many mold issues based on wet air and negative buildings.

 

[jspath2339]

The old school way is "very positive". The buildings back in the day were very leaky, and the best way to ensure that the space is conditioned to the temperature you expect is to provide a lot more air at the temperature you want, than the outside will fill back in.

Now, as the buildings have become more and more leak tight this has become less important. It also depends on your climate.

In general I would recommend maintaining a neutral pressurization in a building, but positive in regularly occupied spaces. For example, a typical open office should be positively pressurized to keep the temperature comfortable in that space. However when you consider the adjacent bathroom to the space, the building is close to neutral. If you need to make a choice, definitely err on the side of slightly positive however.

If you're working on a hospital, figure out what room you are designing and what the requirements are. This post was a recommendation for a simple office building. If you are working on anything in a hospital/lab/mission critical space, you should not be going by rule-of-thumb suggestions by people on the internet.