Mold Containment Class, Scrubber CFM, and PPE
The IICRC S520 containment classes, the plastic build, the air-scrubber size in air changes per hour, the negative pressure target, the PPE level, and the disposal and clearance sequence for a remediation job.
Containment class comes from area and category: Class 1 under 10 sq ft, Class 2 from 10 to 100 sq ft, Class 3 over 100 sq ft, a plenum, and a Category 3 job. Scrubbers are sized to 4 to 6 air changes per hour inside the containment.
How the math works
- Categories and classes (IICRC S520): water Category 1 is clean water, Category 2 carries a significant contaminant, Category 3 is grossly contaminated sewage and flood water. Containment Class 1 is a spot under 10 sq ft, Class 2 is 10 to 100 sq ft, a wall, a cavity, Class 3 is over 100 sq ft, a plenum, a cavity system, a Category 3 job, and the class governs the enclosure, the PPE, the filtration, and the clearance.
- Containment build: 6-mil plastic over the floor with a 6 ft lap past the work, taped seams with 12 in laps, plastic 6 ft up the walls on a Class 2 enclosure, plastic to the ceiling on a Class 3 enclosure, a decon chamber at the entry with a zipper, the HVAC openings taped, the door sealed, and the containment in place until the clearance pass.
- Filtration: HEPA air scrubbing sized to 4 to 6 air changes per hour of the containment volume, negative pressure on a Class 3 enclosure with the scrubber exhausting outside the enclosure and make-up air at the far zipper, local exhaust at the cut, a shrouded HEPA vacuum for the surfaces, and no unfiltered air to the occupied space.
- PPE (S520 Annex M): Class 1 takes an N95, eye protection, and gloves; Class 2 takes a half-face or full-face respirator with P100 filters, a coverall, gloves, and eye protection; Class 3 takes a full-face powered air-purifying respirator with HEPA filters, a hood, a taped suit, boot covers, doubled gloves, and a doff sequence in the decon chamber.
- Disposal: bag in 6-mil plastic inside the containment, seal and wipe the outside of the bag before the bag leaves, dispose under local construction and debris rules, sewage-contaminated material handled to the local Category 3 rule, and the disposal receipt, the manifest, and the disposal record kept in the job file.
What are the mold containment classes?
Class 1 is a spot under 10 sq ft: no full enclosure, a plastic floor drop, and light PPE. Class 2 is 10 to 100 sq ft, a wall, a cavity: a poly enclosure 6 ft up the walls, a decon chamber, HEPA scrubbing, and P100 respirators. Class 3 is over 100 sq ft, a plenum, a cavity system, and a Category 3 job: full containment to the ceiling, negative pressure, a double decon chamber, and a powered air-purifying respirator (IICRC S520).
How many air changes per hour does a containment need?
4 to 6 air changes per hour of the containment volume, sized with a HEPA scrubber: a 10 ft by 8 ft by 8 ft room is 640 cu ft, so 43 to 64 cfm, and the scrubber runs continuous through the work. Class 3 enclosures run negative, exhausted outside the enclosure, with make-up air at the far zipper.
What respirator do the crew need?
Class 1 takes an N95 with eye protection and gloves, Class 2 takes a half-face or full-face respirator with P100 filters, a coverall, gloves, and eye protection, and Class 3 takes a full-face PAPR with HEPA filters, a hood, a taped suit, boot covers, and doubled gloves (S520 Annex M).
When is the job done?
The removal is complete, the drying is complete, and the visual is clean: no dust, no debris, no moisture, and the material moisture readings are within 1 percent of the dry standard taken from an unaffected reference surface in the same building. Class 2 and Class 3 jobs end with the containment down after that pass, and a client can ask for a tape-lift, a dust wipe, and an air sample.