HEPA vacuums, sanding and blasting

In plain English

HEPA vacuuming is the workhorse of mold cleaning. R520 specifies professional units that actually filter 99.97% of particles at 0.3 microns. It warns that some consumer vacuums sold as HEPA leak around seals and do not reach that level, and suggests checking units with a particle counter. Standard shop vacuums blow fine spores back into the air and should not be used for most mold work unless vented outside or otherwise controlled. Vacuums should be serviced inside the airflow of an air filtration device, and sealed and wiped before leaving containment.

When growth has penetrated wood, abrasive methods may be needed: hand sanding with dust collection, wire brushing, orbital sanders, or media blasting with sand, soda, sponge or dry ice. Each produces heavy airborne dust, so HEPA negative air with its intake near the work is set up first, and eye, skin, hearing and respiratory protection are essential.

Dry ice blasting leaves no grit behind, but it gives off carbon dioxide that can push oxygen down to dangerous levels in a crawlspace or other tight area. R520 requires continuous oxygen monitoring there, outdoor exhaust of the CO2, and supplied-air or self-contained breathing equipment if oxygen runs low. Other media bring their own problems: sand is the most aggressive and can damage surfaces, soda takes a long time to clean up, and reusable sponge media should be discarded after mold work so it does not carry contamination to the next job.

Key points

• True HEPA means 99.97% capture at 0.3 microns.
• Not every vacuum labeled HEPA performs as one.
• Set up negative air before any sanding or blasting.
• Dry ice blasting can deplete oxygen in a crawlspace.
• Clean and seal tools before they leave the work area.

Official text

This topic is covered in our own words because the standard behind it is copyrighted; we cite it below rather than reproduce it.

Citations

• IICRC S520 Reference Guide, IICRC S520 Standard and Reference Guide for Professional Mold Remediation — Reference Guide — Ch. 5, pp. 61–63. Best practice
• IICRC S520 Reference Guide, IICRC S520 Standard and Reference Guide for Professional Mold Remediation — Reference Guide — Ch. 11, pp. 115–116. Best practice

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