HEPA (High Efficiency Particulate Air) filters are used to filter the air going into clean labs and their laminar flow hoods. They are generally protected by pre-filters, which remove the worst of the airbourne particles, so that they don’t clog the HEPAs. 

With our lab building works hopefully finally complete, it’s been time to change the HEPAs, which have become clogged with dust from the building works. The two pictures show the old and new HEPAs within the grey plastic case. The white HEPA (in the plastic bag) is the new filter, while the black HEPA shows how much dirt has been collected on the filter over the last two years. Perhaps we should charge the city of London for cleaning up their air for them!