A kitchen exhaust system is generally composed of three parts: The plenum, a duct and a fan. The plenum is a box-like structure above the stove(s) that holds metal filters (for straining grease out of the air being sucked in). Occasionally, the plenum has a self-washing system in it – so no filters are required.
The duct normally rises from the plenum and exits from the roof where it connects to the fan. In a single-storey building, the duct can be several feet long. In a large facility, it can be a 100 feet long or more. However, even a simple establishment can be cursed with an exhaust duct that twists and turns above the ceiling, making it harder to reach for cleaning.
Kitchen exhaust cleaning is almost never done in-house for a number of reasons. Each day, particles from the kitchen are being pulled into the duct and slowly deposited on the interior surfaces. It is a very dirty work if one does not have the proper equipment. It also requires mechanical knowledge from the fields of sheet metal and ventilation.
Cleaning methods vary, depending on the location and the governing fire code. The most common approaches are power washing or scraping or a combination of both.
One of the tragedies of the kitchen exhaust cleaning industry, however, is that poor workmanship is commonplace. Clients rarely inspect the cleaning and ducts are well hidden generally. So it is not hard to cut corners without being noticed (at least until the big fire happens).
Some tips that can help avoid poor service include:
- Watch for a quickie job. The most common observation of bad workmanship that we hear from clients is, “He was here for only 15 minutes.” Even the smallest of exhaust systems takes a minimum of 40 minutes to an hour to clean.
- Is the service technician covering up the stoves or grills when he cleans? Grease falls down from the ducts when they are being cleaned and it has to land somewhere. If power washing is being done, plastic sheeting should be very visible around the cooking equipment. If no effort is being made to cover cooking surfaces, that is a bad sign.
- Is he going on the roof where the fan is? This is a must for cleaning exhausts except in the rare instance where the fan is on an outside wall. If the serviceman never asks for the keys to the roof or never takes out a ladder, he’s skipping a major portion of the job.
- Go on the roof and look at the fan (the one that has cooking vapours coming out). Turn it off for a moment. It should not have heavy accumulations or dripping grease after a cleaning. Some discolouration or scrape marks are normal but thick layers of grease should not be visible anywhere.
- Remove a panel. They are commonly on the roof and are not hard to take off. They usually slide off or are held in place by several screws. Simple, one-storey facility commonly has a slide panel at the top of the duct that can be removed, exposing the full interior of the vertical duct to view. Again, heavy grease accumulations should not be visible right after a cleaning.
- Is the company not showing up for appointments or failing to return when they are supposed to? If you are on a quarterly service, are they showing up in three months or is it eight? Poor scheduling implies lack of attention to other details as well and you need your service done regularly to keep the fire hazard to a minimum.
- Are you paying too much by being serviced too often? Some companies clean a duct system monthly when it is needed only once a year. Common cleaning frequencies include:
- Charcoal broilers, barbecues, high-volume cooking: Monthly
- Average kitchens (such as a basic restaurant): Three months
- Pizza kitchens, baking, moderate cooking: Six months
- Low volume (senior centres, seasonal businesses, part-time kitchens): Annual
Statistics show that the number one source of fires in eating establishments is the cooking equipment. Poor exhaust cleaning is not only a waste of money, it also puts the building at risk of fire.Dan Stradford Chief Executive Officer of Action Duct Cleaning Co. Inc. (www.actionduct.com)