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How to Clean the Inside of a Range Hood

How to Clean the Inside of a Range Hood

4 Important Reasons to Keep Your Exhaust Range Hood Clean

Kitchen exhaust hoods and fans can get dirty quickly and there are some really good reasons to clean them thoroughly and frequently.  The first is safety, fire safety to be specific. Let’s say you had a fire break out on one of your kitchen appliances (a stove top, grill, oven, fryer, etc.) and you had a layer of grease built up in the hood, duct, and fan.  That grease is combustible and since heat rises, it will be the first thing to ignite if the fire isn’t put out quickly. It gets even more serious from there. A fire needs three things to burn. 1. Heat (already provided by the fire that just broke out on your stove top), 2. Fuel (that’s the grease that you didn’t get around to cleaning in your hood and duct), and 3. Oxygen.  The exhaust system is designed specifically to provide a high flow of air to keep all those vapors from your cooking from filling the kitchen and eating areas. So as the fire catches in your hood, the exhaust system will act like a bellows and the fire will just roar up through the ductwork and to the roof of your building. By this point you will be evacuating the building, calling the fire department, and hoping you have good insurance.  And in a worse case scenario, someone could get hurt or die.

If the above example wasn’t good enough reason to keep up on hood cleaning, a second compelling reason is that many (probably most) states require the hood to be cleaned by law.  This is for good reason. As you can imagine, if a neglectful restaurant manager causes a fire, it can put the public at risk of death or injury, and other properties at risk as well.  So if the State authorities discover that you are not in compliance with the local laws, you are likely to be fined and possibly shut down until the situation is remedied. The fines will add up quickly and the lost revenue from being shut down is going to hurt.  Aqua Jet is located and operates in Utah where the State has adopted the NFPA 96 “bare metal” standard. This is a common standard, and to see what your state uses, check your local fire marshal website. To sum it up, the standard basically states that when the hood is cleaned it must be cleaned down to the bare metal throughout the ENTIRE system.  So you aren’t going to pass inspection if you just clean the hood and filters.  You will also need to clean the plenum, duct(s), fan(s), roof top, and everything under the hood.

The third reason to keep your hood clean is that many insurance companies require the cleaning.  You may want to check into your insurance policy, because if you have a fire and hadn’t kept up on your cleaning and don’t have records that it was cleaned by a licensed professional, it’s possible that your insurance may not cover the damages.  One instance of this happening would put many owners out of business for good.

The fourth reason is a little less dramatic, but also has an impact on revenue.  A clean hood looks good and gives your patrons, employees, and business associates a sense that you keep a clean kitchen. They will infer that if you take care to keep your hood nice and shiny, you are more likely to take care not to let salmonella or e-coli get into their food.

In short, frequent and thorough hood cleaning can save lives, save money, and make you look good and your customers feel good.

So You’ve Decided to Keep Your Hood Clean….

Here are a some considerations before you put on the coveralls and start scrubbing:

The first thing to consider is that your state may require that the hood system is cleaned by a licensed professional (this the case in Utah and many other locations).  If you are thinking about doing it yourself, then you should check local laws and requirements before getting started. As mentioned before, Utah requires licensing, and most owners’ and managers’ time is better spent managing their kitchen and business than cleaning their hoods, so they choose to hire a third party to do the cleaning for them.  However, if you still want to do it yourself and are located in Utah, then you can learn more about how to get your license on the state fire marshal website.  

There are a few common ways to clean the system and they are outlined as follows:  

Power Washing

This is the most common method and usually the most cost-effective.  However, it requires some specialized equipment and training. Unless you have a small hood with a short and straight duct, a small pressure washer like the ones you can pickup at Home Depot will probably not do the job.  Cleaners who are serious use pressure washers that have 3,000 – 4,000 PSI with 5-8 GPM (gallons per minute) and have steam cleaning capabilities. The heat makes a big difference when getting the grease off. In contrast, the pressure washers you buy at the local hardware store often max out at about 2,500 PSI and 1.5 GPM, and heated units aren’t commonly available.  The GPM is a crucial component to the cleaning capabilities of the machine, as it allows you to clean a larger surface area and has more washing force to bear into all the grease buildup in the hood. The price difference between the two types of machines is stark too. The one at the hardware store might cost you $200, but a professional grade version would start at close to $4,000.

Manual Cleaning

The advantage to manual cleaning is of course that you don’t need specialized equipment.  The cons are that it is much more time- and labor-intensive and can easily cost you more than the power washing option.  Also, there are areas in the system that will be hard or impossible to reach and clean by hand that a high-powered, steaming-hot jet of water can make short work of.

Brush System

There are brush systems on the market that can be used as well.  These typically consist of a robotic rotating bush that will crawl through the duct work and clean as it goes.  A pressure washer is then used to clean the hood and fan. This system is well suited for long and complicated duct work.  However, the downside is that is it very expensive (usually in the range of $50,000 to $100,000 for the setup).

How to Clean the Hood System With a Pressure Washer

Since power washing (or pressure washing) is the most common and usually most cost-effective method, and it is the method of choice for Aqua Jet, this article will focus on how to clean the hood system with a pressure washer.

The first problem you have to deal with is that all the water you are spraying while cleaning has to go somewhere, and most restaurant managers don’t want it all over their kitchen.  The way to deal with this is to mask off the hood with plastic sheeting (sometimes called Visqueen) to contain the water. Find an effective way to attach the plastic to the outside of the hood and then you can funnel it down to a drain if one is available (usually there is not) or you can funnel it into a large garbage can.  Be sure to leave an opening in the masking to get in and power wash. For a typical 10 foot hood it would take a team of two experienced people about hour to do the masking. If it’s your first time give yourself an extra 2-3 hours to get things figured out.

Once you have your masking set up, spray a strong soap on all areas of the inside of the hood.  While the soap is soaking you can then go to the roof and begin cleaning the fan(s) and duct(s).  You will want a soap that has some serious grease cutting capabilities. Most commercial degreasers still aren’t strong enough.  You’ll be best suited to use something designed specifically for applications like this.

Most exhaust systems use a standard bell fan.  These fans are built for the weather and you can simply soap and power wash them.  You need to clean the top, inside, bottom, and fan blades. To clean the underside and fan blades you can simply lift the fan off its base.  Many fans come on a hinge kit that makes for easy cleaning and servicing and you can simply unlatch and tilt the fan over. For fans without a hinge kit, you may have to unbolt and lift them completely off the duct.  Be careful not to pull or strain any of the wires connecting the fan to the rest of the hood system.

Once you have cleaned the fan, then move on to the duct.  It is a good idea to have someone down below to keep an eye on the water and make sure your masking doesn’t tear or fall down.  Soap and power wash the duct down to the bare metal. When you are done with that, replace and secure the fan and clean the grease off the roof with the pressure washer.

Next you need to clean any access panels in the duct.  There should be one at every bend and at any portion of the duct that is longer than 10 feet.  There are many hood systems that have not been installed properly and don’t have the required access panels.  If you don’t have the proper access, call up an HVAC service company and get some installed. If you are in Utah, Aqua Jet can do this for you, usually at a much cheaper rate than an HVAC company would charge.  You will be amazed and disgusted at what builds up in there if it hasn’t been cleaned for a while or there aren’t proper access panels.

Once the duct is clean, then move to the hood and power wash it out.  Be sure to get in all the nooks and crannies and hard-to-reach spots up in the plenum area.  Any grease left in the system is a potential fire hazard. The filters can also be simply soaped and sprayed with the power washer.  After you have it all clean, take down your masking and clean up.

If you decide that this sounds like more work than you want to take on, give Aqua Jet a call!  We pride ourselves on providing the highest quality cleaning service and will provide Completion & Deficiency Reports required by the fire marshal, and before and after pictures of the fan, duct, and hood.  We also make sure to mop the floors and polish the hood when we’re done, making you look good for the fire marshal and your customers.

How to Clean the Inside of a Range Hood
How to Clean the Inside of a Range Hood
How to Clean the Inside of a Range Hood

Visit the rest of our site to view more pressure washing tips and tutorials.

If you currently live in Utah and are needing services to help you clean your commercial kitchen range hood, contact our sister company, AJET Services (801-330-0398 or

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