Why the kitchen is still hot with the exhaust running
The range hood is running flat out and the kitchen is still unbearable. What is wrong?
Published 28/09/2026. Written by the Pristine Cooling team, Kalgoorlie.
The exhaust is probably working fine. A range hood can only throw out as much air as the kitchen is able to let back in, so if there is no path for replacement air the fan ends up pulling against a partial vacuum. It then moves a fraction of what it is rated for, no matter how loud it sounds. The hot kitchen is usually a make up air problem rather than an extraction problem, which is why fitting a bigger fan tends to make it worse.
Here is how to tell, in about thirty seconds.
The test
Prop the back door open.
If the kitchen noticeably improves within a minute or two, you have your answer. You just gave the hood somewhere to draw from. That is not a fix, it is a diagnosis.
The other tells, all of which mean the room is under pressure:
- The back door is hard to pull open, then slams itself shut
- Air whistling under a door or through a gap
- Gas appliance flames looking unsettled or leaning
- Steam rolling out past the edges of the hood instead of being caught
- The hood sounding like it is working much harder than the air movement suggests
Where make up air is meant to come from
Air taken out has to be replaced. In a kitchen set up properly that replacement is deliberate: a dedicated make up air unit feeding tempered air near the cooking line, transfer grilles from the front of house, a louvre, sometimes a combination.
It is not an afterthought. It is sized against the hood, because the two are one system pretending to be two.
What usually went wrong
Kitchens change. The hood does not.
A fitout gets reworked, a serving hatch gets closed in. A roller door gets replaced with a solid one. Someone seals up a wall vent because it let dust in. The hood gets upgraded to a bigger one without anybody touching the supply side. A new fryer or combi oven goes in, so the load went up while the air path stayed the same.
Every one of those is a change to one half of a balanced pair.
Why a bigger fan is the wrong instinct
More extraction against the same closed room means more vacuum, not more airflow. You get more noise, more power drawn, more wear, roughly the same result.
There is a safety dimension too. A kitchen under enough negative pressure can start pulling air back down the flue of gas appliances instead of letting combustion products go up it. That is not something to work around with a bigger fan. If the flames on your gas gear look wrong, stop guessing, get someone in.
The ordinary faults, which are also worth checking
Not everything is make up air.
Filters loaded with grease choke the hood, because air cannot get through them. They are the most commonly neglected part of a kitchen, then the first thing to check. A slipping or broken belt on a fan makes the noise without the airflow. A damper stuck shut does the same. Wiring reversed after electrical work will run a fan backwards, which looks and sounds completely normal while doing nothing.
What we actually cover
Range hoods, the fans, the ductwork, then the make up air that balances against it. Supply and install, servicing, breakdown repairs.
Kitchen exhaust sits on the same 24/7 line as refrigeration, which matters more than it sounds. A kitchen that has gone unworkable at seven on a Friday is a kitchen that is not trading, so it is not a Monday job.
The rest of a building's ventilation is the same conversation: toilets and amenities, car park and plant room exhaust, workshop extraction. Usually the same ductwork, usually the same fans, usually the same reasons it stops doing what it is supposed to.
On an existing kitchen we can test it, find where the air is going, then put right what is faulty.
What to do now
Check the filters. Do the back door test. Look at what changed in the room since the last time it was bearable.
If it is the filters or a belt, that is a service visit. If the back door test transforms the room, the conversation is about make up air, which is worth having before another summer.
More on what we cover is on the ventilation page. On a build or a fitout it usually comes in under mechanical services. Gear that gets looked at on a schedule fails less, which is the whole argument for preventative maintenance.
Related pages
Ring us and we'll tell you when we can be there
Same number either way. Ring it if something is down right now or if you want a quote, a service or a maintenance contract set up.