① Is the power plug securely inserted in the power outlet?
→ Reinsert the power plug into the power outlet.
② Has the filter been taken out of the plastic bag when it was installed?
→ Take the filter out of the plastic bag and install it again.
③ Is the air inlet or outlet of the base unit or the pre-filter contaminated?
→ Clean the unit to clean contamination off the air inlet or outlet as well as the pre-filter. If the condition does not improve even after cleaning the unit, replace the filter with a new one.