How to stop condensation in a stainless steel range hood

Is your stainless steel rangehood dripping? Nothing’s worse than finding oily liquid dripping from your hood. It’s unsanitary and annoying to constantly clean.

The source of this dripping is almost always condensation which is forming inside the duct and running down it, which then drips out of the range hood.  

A commercial kitchen exhaust system should not be dripping with condensation, and there are ways to stop it. Below we’ll explain why condensation forms and how to prevent it.  


Why does condensation form in stainless steel range hoods? 

Condensation forms inside the ducts of range hoods when hot air comes in contact with a cold surface. In this case, the cold surface is the duct of your range, and the hot air is coming from cooking on the stove which is heating the surrounding air. Condensation in the range hood duct is more common during cold weather, as this is when the duct is likely to be colder. The range duct could also be cold if you have your air conditioning set very low, and enough of this air is reaching the duct. 

Condensation is more common in induction stoves, rather than in gas stoves. This is because induction stoves heat only the cooking pot and its contents—they don’t heat the surrounding air. This means hot air isn’t going into the duct and heating it (which would make conditions impossible for condensation).  Instead, only the steam from cooking is going up into the duct, and this will create condensation. Gas stoves, on the other hand, heat up the surrounding air, and this air in turn heats up the duct—meaning condensation can’t be created. 


How can I prevent condensation from forming on stainless steel range hoods? 

There are several ways you can prevent it, and there’s a good chance you won’t have to splash out on expensive fixes to stop condensation. Check out these ways to stop condensation from forming in your range hood: 

Check the dampers 

One of the most common reasons people find condensation dripping from their range hoods is that their dampers are broken, missing, or incorrectly installed. A damper is a plate with flaps that regulates the flow of air—preventing outside air from entering the duct but still allowing the duct to exhaust. 

 A properly installed range has two metal dampers—one at the top of the range hood where it connects to the duct and one at the wall where the duct exhausts the air.  The damper plates never create airtight seals because they must allow exhaust air to exit even with the fan working at low speed. But they should be preventing any drafts from coming in.  

It’s important to check the dampers and make sure they are operating as they should. Sometimes the duct has an exterior cap that prevents rain from entering. If there is one of these and your exhaust duct exits out of a side wall, it will have a spring that holds the damper shut when the fan is off. If the cap seems faulty in any way, consider replacing it. If you have a roof exhaust, there should certainly be a cap to prevent rain from entering, but it won’t have a spring to check. In both cases, check if the damper is blocked somehow or bent.  

Then take a look at the damper of the range hood. To do so, you’ll need to remove the section of ducting that the range hood is connected to. Usually, you’ll find a butterfly damper that has two metal flaps that pivot on a horizontal bar. You’ll also find a hood grease screen—remove it and give it a good clean with a degreaser. You may wish to give the whole area a clean like this. With the screen still removed, turn the fan on and off again to test that the damper is opening and shutting freely. 

Additionally, check that there are no screws that are interfering with the movement of the damper flaps as these can sometimes be installed incorrectly. If there is any damage to the damper, you should replace it. Oftentimes, replacing faulty or missing equipment in the range hood, duct, and exhaust vents can stop any condensation. 

Read more about the importance of routine restaurant hood maintenance and repair. 

Wrap insulation around the duct 

This is a fairly cost-effective solution for stopping condensation in the exhaust duct. By wrapping insulation around the duct, you should be able to prevent the duct from getting overly cold and create conditions where condensation is able to form. Specialist insulation for this exact purpose exists and is quite easy to find. 

Run ducts through the wall 

If you’re yet to install your exhaust duct, or you want to install a new one, carefully consider where the duct will run. Running the exhaust ducts through the roof means the duct will be at a vertical angle. This means condensation can run down the duct and out of your range hood. By going through a side wall, you can avoid this because the duct will run at a horizontal angle, preventing condensation from being able to drip out the hood.  

Avoid creating any corners in the exhaust where condensation will collect 

If you must install the exhaust duct through the roof, do it so that there are no loops or corners that will collect condensation. If there are any, condensation could collect in them on the lower areas and mould will begin to form. 

Install insulated ducting 

Instead of separately purchasing duct insulation, you can buy ducting that is already insulated. This can save you the trouble of buying and installing the insulation separately. 

Ensure your exhaust hood fits properly in the roof vent 

If you are running the exhaust through the roof, it’s crucial the duct properly fits the vent. If you jam the duct in, there won’t be an airtight seal, and it’s highly likely that condensation will drip back down through the range hood or drip into the ceiling/attic space, creating mould. Instead, use a roof exhaust hood that exactly fits your exhaust ducting—one that allows you to fasten the ducting to the hood, creating an airtight and solid seal.  

Choose an exhaust hood that has an internal drain path 

Some roof exhaust hoods have internal drainage paths so that any condensation that gathers is directed out onto the roof, and not back into the attic space or down the duct. 


Condensation dripping out of your stainless steel rangehood is preventable, and it shouldn’t be accepted as a normal occurrence. If the above advice does not solve your issue, or you need additional guidance, get in touch with Allfield commercial refrigeration, Perth. 

The team at Allfield are experts in commercial refrigeration repairs, Perth. We can service and repair all types of refrigeration systems, air-conditioning, and mechanical service equipment. Have a chat with the team today. 


1800 265 337