Thursday, December 22, 2005

Mold Remediation Ventilation

BrooklynDodger comments: The Dodger recently mused on protective schemes for airborne aerosol biologic agent exposure, with emphasis on Katrina related mold. [The Dodger believes this is the first internal reference to a BrooklynDodger blog posting.]

Mold remediations these flooded homes, or restorations in general, are "just" remodeling projects in small homes. Obvious protections are basic construction standards. Those standards require a competent person and training in hazards for all employees, although these general standards are rarely enforced by OSHA. The most convenient way to deliver these requirements would be a 30-hour construction card for the supervisor and 10-hour cards for the workers. Dream on.

But there are specifics where mold is being disturbed, which under the plain language of HAZWOPER should be covered by the standard.

The Dodger notes lack of recommendations for ventilation during mold remediation or other construction projects.

Let's imagine a room 20 ft x 50 ft with a 10 ft ceiling, which could maybe be a floor of a small house. Thus, 1000 sq ft and 10,000 cf. The Dodger measured the exhaust volume of a $15.00 [on sale at hardware store], 20 inch square window fan at 1000 to 2000 cfm; they move surprising amount of air against no static pressure. Thus, 1 cfm/sq foot and a 10% volume/minute replacement rate, or 6 air changes per hour minimum [yes, the Dodger knows air changes per hour is dislike terminology.]

[Houses have less volume per outside dimensions because the ceilings aren't usually that high, and interior volume is taken up by walls and other structures.]

[By contrast, a modern air conditioned office is designed for 1 air change, but it's mostly recirculated air.]

The 6 air changes is better than most factories have for general air. The fan would have to be framed into an open window with duck tape and cardboard. If you wanted better ventilation, you could spring for two, the cardboard with lying around and there's plenty of tape left on the roll. [Square shape of the housing is a benefit here, it would be require more crafting for a round fan.]

The point here is that lots of exposure is aerosol hanging in the air; mold spores may be generated continuously by the fruiting bodies, but dust is not being generated continuously, and the fan could clear them out and reduce reliance or improve effectiveness of a respiratory protection scheme. Workers standing parallel to the general flow of air would get some additional protection.

The fan is only generating about 5 fpm through the plane of the 10 x 20 short axis of the room, but would be generating upwards of 100 fpm through a doorway, which would certainly contain dust within a room. Plastic sheeting in the door would increase containment.

The Dodger applied this scheme during floor resurfacing in the Dodger's home. It worked great until the resurfacers, not understanding, turned off the fan.

The difference between mold remediation aerosol and asbestos remediation aerosol is that mold particles are less durable, and found in the environment anyway [that's how they got to seed the inside of the building to begin with.] Those who wish containment could tape a HEPA furnace filter to the back of the fan, which would cost some volume.

1 comment:

Anonymous said...

I usually use the asbestos standards for mold remediation-- full hepa, negative air, suits, decon & site control--expensive, but ZERO incidence of worker injury or spillover past the containment

--nyc enviro safety guy