# Interest group forums > Food Industry Forum > [Question] Extraction System

## AmithS

Hi Guys & Gals,

What sort of maintenace do you do on your extraction systems?

I know you need someone to clean the entire system once a year.

I also get my staff to walk the metal filters every 1\2 weeks after soaking them in hot water and de-gresser.

Is this the best method ??

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## adrianh

There are various types of extractions systems in use today.

1. Dry - simply vents straight to atmosphere i.e. Cyclovent
2. Water wash i.e. Cyclowash
3. UV i.e. Reactovent

Dry systems are the dirtiest - their ducts are very dirty and they also spill a lot of oil onto the roof. If it is possible you should remove the filters once a week and degrease them. You should also chech & clean the fire dampers to ensure that they are always operational.

Water wash systems remove a lot of oil from the system. A lot of oil is trapped and goes to the oil traps. The system should automatically run a wash cycle at night for 5 minutes using hot water & and a detergent like GP300 to clean the spray heads & filters. Check that the oil traps are cleaned daily and that the water traps are clear. You should also check that the detergent is actually being pumped into the system during the wash cycle. This is easily done by checking the detergent level on a daily basis. Remove and clean the filters on a daily basis. Check the fire dampers! You should also check that the water pressure is ok and that your geyser is operational. We have a manual override on the PLC based systems that allows you to run a manual wash cycle. The manual wash cycle will show whether the cold & hot water flows, the dosing pump works and that the electro-valves operate correctly.

UV systems. These systems are the cleanest of them all. The tubes in the systems emit UV-C radiation. The tube creates a huge amount of Ozone ( 03 ) (Oxygen with an extra atom which makes the molecule very unstable) The extra oxygen atoms combine with the oil to break the oil down to CO2 & H2O. CO2 and steam is emitted via the exhaust. The UV-C also destroyes bacteria and smells. The frequency of UV interferes with the DNA of bacteria which esentially kills the bacteria. UV-C automatically keeps the canopy and the ducts clean. If the UV system is operational the inside of the canopy will have a slight white powder coating - nothing else. You need to remove the baffles on a daily basis and remove the filters. Then you need to check the inside of the canopy and ensure that all the oil gets burnt away. You must check that the UV tubes are clean and that the fire dampers are clean. You simply turn the filters round and put them back (the UV will clean them automatically). You should also run the sytem and walk around and try to smell the ozone. If you do then the system is either creting too much ozone or you have a leak in the duct.

If you are running an ecology unit you need to follow the manufacturers recommended filter replacement period.

99% of problems with extraction systems are due to poor preventative maintenance. Check the system on a monthly basis. I've seen restaurants get smoked out because of neglect. Another thing that I insist on is a mechanism to override the wash systems and keep the fan running if the wash system fails. You can always fix a wash system in the morning but you can't leave the smoke till the morning.

BTW: I've seen a company clean a duct at the V&A and forget to put the duct side cover back. Numerous stores complained of a fishy smell which led to a huge investigation. The duct cleaners also tend to turn the water off and forget it off. I've even had to reprogram PLC's because the cleaning couldn't figure out how to stop the system so the simply trashed the settings of the PLC. And yes, the PLC was password protected.

Ducts must be checked anually. If you run a dry system then you should check the ducts every 6 months.

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## AndyD

The problem with extraction systems is you only find out how important they are when they stop working. I would suggest you keep a spare fan unit for emergencies. The fan should have a life expectancy of 5-8 years if it's kept clean. The only maintenance you can really do is weekly filter cleaning and the accessible areas of the hood. Always make sure the fan is OFF whilst any filters are removed. Twice a year you'll need to get a reputable duct cleaning company to clean the rest of the system.

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## adrianh

Have you seen the size of some of the fans? 

I am yet to see a fan that is small enough to keep as a spare!

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## AndyD

I know several large restaurants and hotels that keep a spare fan. Their desire to do so is normally brought on by a day or two without one. You're right, they're fairly large and expensive but when they look at the cost per hour/day without trading it's a good investment. Often they have the old unit rewound when a replacement has been fitted.

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