First, the ANSI/IICRC S500-2021 Standard for Professional Water Damage Restoration states,

“Filters should be replaced as necessary following manufacturer’s guidelines to maintain performance efficiency.”  This doesn’t mean the insurance carrier owes for HEPA filter replacement because there are many variables that need to be considered, including on how well the unit was maintained by the restorer, that determines whether they should be replaced or not.

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For reference this is what the S500 says about HEPA filters, “Air filtration device (AFD): AFDs consist of a motorized fan, filter(s), and housing, designed to remove airborne contaminants from the process air stream. AFDs typically have a series of filters consisting of pre-filter(s) and a HEPA filter. Also referred to as an air scrubber or negative air machine (NAM) depending upon the application.”  Remember, the pre-filters (primary and secondary) should be changed often when they become dirty because they are installed to catch large particles, like drywall dust, debris, etc. Typically, a piece of filter media (primary) is laid on top of the cotton pleated filter (secondary) to catch as many of the large contaminants as possible.   These should be changed often.  The Xactimate description states that replacement of the primary and secondary filters are figured in with the daily rental cost for the AFD and should not be charged extra for.  The more expensive HEPA filter should only be changed when it is dirty enough to restrict airflow to the extent the unit won’t provide the correct number of air changes per hour (ACH) called for.

Regarding manufacturer guidelines, one manufacturer actually stated in their manual in 2004 to change the HEPA filter after every water job, but this was ridiculous and was added to help sell HEPA filters. Since then, that manufacturer has changed their guidelines to state, change the HEPA filter after every remediation job.  This is more reasonable, but changing the HEPA filter still depends on how well the unit is maintained (pre-filters changed often enough, dust suppression devices utilized during demolition, negative air pressure maintained inside the chamber, etc.)  Other AFD manufacturers state their HEPA filters can last hundreds of hours if the unit is properly maintained and pre-filters changed regularly.  Most AFDs include a "filter change light", but when the light is on it means to change the pre-filters first and recheck and only change the HEPA filter when the filter change light stays on after clean pre-filters have been installed and retested.  This typically calls for HEPA filter replacement only once or twice a year with normal usage and in some cases the HEPA filters could last multiple years for it doesn't hurt the unit to run it with dirty HEPA filters, although if dirty enough it could cut down on your air changes per hour.

In summary, HEPA filters should be changed when they restrict ariflow enough to lose the required amount of air changes per hour AFTER the pre-filters have been changed and the unit retested, typically 4 ACH. I suspect that HEPA fitlers are billed for a lot more than they are replaced.  I ask for photos of the “dirty” HEPA filter at the job site of the job in question and ask them if they changed the pre-filters and tested to see if there was a loss of air changes per hour (ACH)?  I know many vendor programs allow a .1 or .25 towards the replacement of the HEPA filter, but it has been my experience that they rarely get changed, but are often charged for.

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*Remember, to always setup your AFD under negative pressure and record air pressure differential readings to validate, if possible.

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