Because a lot of bagless vacuum

Because a lot of bagless vacuum cleaners are really quite a simple design where the dirt is sucked into a chamber that contains the main filter, their suction relies heavily on keeping that filter clean. The basic design of the Nilfisk Combat Filter is very similar to a car air filter. It is essentially a cylinder shape with the filter material being folded over many times to increase the effective size of the filter. This folding produces a series sample tubes wholesale of V shaped valleys in the filter. These valleys are where the dirt collects and begins to restrict airflow.

The Nilfisk Combat Vacuum has a very basic semi self cleaning mechanism but it is only useful if you use it each time you empty the dirt chamber. If you look at the top of the dirt canister there is a large dial, basically hold the chamber still and give the dial a few turns over a bin. What this actually does is like flicking the inside of the filter to help dislodge the dirt.The most effective way to prolong the life of the Nilfisk Combat Filter is to completely remove it on a regular basis and gently tap the filter on a hard surface as you roll the filter round. If you can still see dirt and debris on the filter you may also need to clean in between the folds of the filter with a tiny brush. 

The brush is effective and as a vacuum technician i have done this hundreds of times in the past. I have to be honest though i don't do this anymore for customers, it is a messy process and I don't know what the vacuum has sucked upIf the filter is really blocked I ask the customer to purchase a new one, or give it a good clean themselves. What I find is that if the dirt is not coming out with tapping then it is probably past it's best anyway.The thing you have to remember is that this filter is the one that allows lots of fresh air into the motor to keep it cool. If the air is not getting through because of a worn or blocked filter it will cause the motor to run hotter than it was designed to. This will in turn result in it wearing out the carbon motor brushes much sooner than expected. The cost of replacing the filter is certainly less than the cost of replacing the motor or the whole machine.

It is worth noting that like most domestic vacuum cleaners the Nilfisk Combat is not a suitable machine to suck up plaster or gyprock waste. Now when i say this to people the response is normally "of course not" and what they mean is they wouldn't use it professionally to clean up a whole renovation. Most people would still use it to clean up a small amount of plaster like if they added a new power point or patched up a hole in the wall. Even this tiny amount of plaster will cause damage it will go through the filter and directly go into the motor bearings and brushes. I have literally seen a new vacuum burnt out after 1 use to clean a small mess like this.If you are stuck and need to use your machine for something like this be prepared to buy a new filter straight away. I have serviced about 20 of these machines in the last couple of years and in 80% of these repairs the problem was caused by poor filter maintenance.SO in a nutshellIf you want to get the best suction and value from your Nilfisk Combat vacuum cleaner you need to pay regular attention to the Nilfisk Combat Filter!