The range filter in a kitchen is more important than many restaurant owners and managers realize, unless they work over the stovetop themselves. When that filter is dirty or not functioning well, the kitchen gets warmer and smokier and grease may actually drip from the filter onto the stove itself. Note some answers to commonly asked questions about these filters in a commercial kitchen so you know yours is always properly cleaned and maintained.
What is considered a clean filter?
Typically a clean filter means one that is down to the metal; there should be no grease or other debris on it. This isn't always possible to maintain since of course the first time you cook under a clean filter, it will catch some smoke, grease, oil, and other such debris and be technically dirty.
However, if you can't see much bare metal under all that grease and oil, you need to have the filter cleaned even if it's before your legally required cleaning schedule. Remember that the more grease and other debris on the filter, the more risk there is of a kitchen fire. Not only is the grease on the filter flammable but it also blocks and clogs that filter so that smoke cannot get through. To ensure your filter is clean and functioning properly, always clean it when there is less bare metal than there is grease covering that metal.
Can a filter be run through a dishwasher?
Typically the answer is yes, but note that it's good to soak a filter in water and a degreasing detergent first. You may even need to do this overnight. This will loosen the grease on the filter so you can rinse most of it away, and then run it through your dishwasher. If you skip this step, that grease may clog the dishwasher hoses or cause added wear and tear on the dishwasher.
Does a filter still need professional cleaning even if the staff clean it themselves?
This will depend on your own area and regulations for running a restaurant or diner, but note that it's usually still a legal requirement for a professional company to clean and inspect the filter. This might be a monthly requirement or it might need to be done quarterly; the regulatory department that issues business licenses for restaurants can tell you what's required for your business. Note, too, that certain paperwork might be legally required to go with this professional cleaning, which is another reason to never skip having this done properly, so your facility doesn't get shut down by an inspector.