When should you replace your HEPA filter
?
It is a bit hard to determine when it is the right time to change an old HEPA filter.
There are many factors involved including: usage time, air pollution, filter positioning and even humidity.
The recommended time to replace the HEPA filter is between 3 to 6 months which is a very broad average.
In reality, a filter should be changed when its ability to filter a high degree of particles is reduced. If you continue to use a filter that is only 50% efficient, that means it will take around double the amount of time to purify the air in the same room compared to a filter with 99% efficiency.
At AirDeveloppa, we have come up with a little experiment that you can do to know if it’s time to get a new HEPA filter.
You will need:
A PM2.5 meter (such as the AirCheck Mini). A room with a PM2.5 concentration of at least 100ug/m3.
1. Measure the PM2.5 concentration in the room 
165ug/m3 (in this example)
2. Multiply the concentration times 0.05(5%) 165*0.05 = 8.25
3. Place the PM2.5 meter at the air output of your air purifier.
4. The meter should read below the calculated value. A good HEPA filter should filter up to 99.5% of PM2.5.
After months of using the filter, this value will drop. If the efficiency of your filter is below 95% to 90%, then, it is time to replace your HEPA filter.
