Does the HEPA Vacuum Really Work?



(Is Your HEPA Vacuum a Violation of the Clean Air Act?)
You are standing in a room after mold remediation.  Breathing is more difficult.  HEPA filtered air scrubbers have been running for a week.  The industrial hygienist (or other consultant) claims the spore trap test results are lower than outdoor test results.  Your doctor says your biomarkers have taken a turn for the worse.  What’s wrong with this common picture?
Did the HEPA filtration devices leak?  Bob Brandys gave presentation at the IAQA yearly meeting in 2006 (Nashville TN) concerning testing HEPA or High Efficiency Particulate Air filtration units for failure.  This was the start of an Indoor Environmental Standards Organization standard to get ANSI certification.  The IESO is part of the Indoor Air Quality Association or IAQA.  His past consulting work allowed him to see a 20% failure rate of HEPA filters tested with hot DOP (Di-Octyl Phthalate) vapors before installation at a federal research facility.  Bob Brandys was now talking about field testing HEPA filtration devices rather than just filters with a handheld, laser particles counter. 
The first edition (2003) of the IICRC S520 Standard and Reference Guide for Professional Mold Remediation ( stated a need to test HEPA filtration devices with a laser particle counter even though there was no standard for this type of testing.Manufacturers may test the some filters individually but, they don’t necessarily test the machines with the filters to make sure they don’t leak.
In 2007, I started post testing after remediation with an ERMI vacuum cassette directly on the floor with no carpeting.  I had a job with extreme failure after cleaning the same way I had done for years according to the various standards and guidelines.  I cleaned again and retested several times.  Each time I kept removing or replacing different parts of the process to identify the problems. 
One of the problems: my HEPA vacuum was leaking small microbial particles so I was pulling contamination from surfaces and spewing these small particles into the air – some would settle to the floor.  I thought about all the contractors bringing bad equipment from bad jobsites and making other situations far worse.  You will not see this problem with spore trap air samples if you have read my previous articles or understand the limitations of various test methods.  How do we know contractors are not bringing new and potentially worse problems with HEPA vacuums, HEPA air cleaners, dehumidifiers, etc.?  Contractors who perform mold remediation may also do asbestos abatement, sewage clean-ups, crime scene clean-ups with dead bodies (unknown diseases) or biosafety labs.  What are their decontamination practices and quality assurance/ quality control (QA/QC) programs?
This led me to contribute and peer review a book (In-Field Test Methods and Reference Standards for Portable High Efficiency Air Filtration (PHEAF) Equipment) written by Bob & Gail Brandys ( for testing HEPA filtration devices with handheld, laser particle counters.  My professional goal was to get the truth to the unwitting public and force others to get off the fence.  Bob started with the IESO committee in 2006.  In 2010 it became obvious a standard was a long way away while people were suffering.  I sent some pictures published in his book showing Chaetomium spores exiting the exhaust of a HEPA vacuum made by a leading company.  Bob & Gail Brandys assembled a nice list of peer reviewers.  Although the book is not ANSI certified, neither is the AIHA Green Book (Recognition, Evaluation & Control of Indoor Mold) cited my many consultants in the industry.  The IESO ( will have their data one day and publish a standard.  Until that time, we need something to stop watching dogs chase their tails.  We also need to have two sources since we don’t know if the future IESO standard omit the testing of HEPA vacuums until a later revision.
In-Field Test Methods and Reference Standards for Portable High Efficiency Air Filtration (PHEAF) Equipment also addresses ULPA or Ultra-Low Particulate Air vacuums.  You may see some vacuums called “lead” or “hospital” vacuums that claim to filter 99.9% of particles measuring 0.1 micrometers in diameter.  You will need a condensation particle counter to measure this smaller size.  The smallest size particle for penetration in filter media depends on the density of the particle.  Lead and other heavy metals have higher density than mold or many particles you encounter.  Another problem is the design of the exhaust.  Some vacuums have a simple exhaust port.  Others are “rotary exhaust” which means they exhaust in several locations at once.  These are very common and hard to test.
You can use a laser particle counter to measure particulates in the air but, you won’t know the type of each particle or concentration of each type of particle.  This requires some very expensive microscopy using various types of electron microscopy as well as other techniques.  This is much more expensive than ERMI samples.  Most people getting mold remediation work already can’t afford the investigation and remediation of mold and bacteria. It is better to use the laser particle counter and condensation particles counter (for smaller particles from 0.1 micrometers and smaller) to check the HEPA filtered equipment if the contractor is relying on it to clean the surface and air.
It is better to ask the remediation contractor how HEPA filtrations devices are tested in the field or explain how they will use engineering controls to overcome unknown equipment leakage of particulates.  Forget the years of experience, following whatever list of remediation documents, chest of war medals or who they know. 
I will leave you with a thought.  Mold secretes mycotoxins on the surfaces where it grows including paper-faced gypsum board.  Mycotoxins on a surface are not dangerous unless you can inhale the surface in particulate form.  One theory for mold to produce mycotoxins is to act as an enzyme of solvent for breaking-down surfaces so the mold colonies can convert the surface material to food sources and/or allow hyphae (roots) to penetrate the surface.  Mold remediation firms use mechanized equipment to cut paper-faced gypsum board and wood.  This creates very small particles in large quantities in the air and onto surfaces.  The particles may have mycotoxins on the surfaces.  You will still have the same health effects from mycotoxins when you inhale mycotoxin coated gypsum board particles compared to mycotoxin containing mold particles.  Also, paper-faced gypsum board has some heavy metals in the composition which means the HEPA vacuum may not filter these particles since their efficiency is measured as capturing 99.9% of particles measuring 0.3 micrometers in diameter rather than 0.1 micrometers in diameter.
Can your mold remediator see the invisible cloud?

Greg Weatherman is a Certified Microbial Consultant with aerobiological Solutions, Inc.  He has 15 years of experience for consulting and contracting with microbial problems.  He also wrote a chapter concerning testing and remediation of mold in Surviving Mold.  He holds patent #7,951,227 for cleaning particles from the air with AeroSolver. He has more than a decade of experience with Dr. Ritchie Shoemaker’s patients.