The IQAir Replacement PreMax Pre-Filter for the HealthPro Series is a remarkable filter with the power to remove over 90% of the particle weight from the air going through the air cleaner, allowing the IQAir HyperHEPA filter to last up to five times longer than similar filters in ordinary air cleaners.. The IQAir Replacement PreMax Pre-Filter for the HealthPro Series should be changed every six to eighteen months with normal use.