- Home
- Building pressure
Does your building breathe?
Exhaust takes air out. Something has to bring it back. When it doesn't, the building runs negative and the symptoms show up at the doors, the hood and the drains long before anyone calls it a pressure problem.
How likely is negative pressure?
Nothing ticked yetTick what you see and this updates. Any single symptom can have another cause; several together usually point one way.
- We measure building pressure with the exhaust running and idle
- We check hood airflow against the make-up air unit
- We look for back-draft risk at every combustion appliance
Why it happens
Four common causes
- Hood without make-up airA kitchen hood can move thousands of cubic feet a minute. If nothing replaces it, the building pulls air through every crack it can find.
- Make-up air unit switched offThey get turned off when they blow cold air in winter — and then nobody turns them back on.
- Exhaust added laterNew restrooms, welding bays or spray areas add exhaust that the original design never allowed for.
- Sealed-up buildingsRe-roofing, new windows and weatherproofing all reduce the leakage a building used to rely on.
The safety part
Negative pressure can pull combustion gases back down a flue instead of letting them out. That is the one symptom on the list we treat as urgent: if a flue smells, or a water heater keeps going out, stop using it and call someone the same day.
We check draft at every combustion appliance while the exhaust runs, because that is the condition the building is actually in.
