Re: Re: Formaldehyde

[Guest guest]

Henry,

I remember reading about 20 years ago that EPA found 85-90 degrees

with 4 air exchanges per hour for 48 hours reduced " out-gassing " by

80%. I don't know if this was short term or long, as you pointed out.

Regardless, I've been using this as a model for new or remodelled

homes since then.

The criteria for success is the structure becomes habitable for the

susceptible occupant. They report that neither heat nor air exchanges

alone is very effective, but both together is sufficient. The closer

the source is to the exterior (or inside a complex structure) the

less likely a " bake-out " is successful. They never attain 4

exchanges/hour, struggling to get 3/day, which seems sufficient to

prevent re-absorption. The typical time - depending on sources,

susceptibility and impact - is 3-5 days. I've had some houses require

more than a week and occasional point sources much longer. Despite

the cost of the time out of the house, I don't know of another way to

accelerate the process of " normal " off-gassing when the impact for

susceptible occupants warrants it.

Carl Grimes

Healthy Habitats LLC

-----

> , Quack -

>

> Ten to fifteen years ago, a " building bake-out " was recommended as a

> method to reduce VOCs. Owners or contractors would heat the building to

> 90 degrees or more for a week or so, then try to flush out the VOCs so

> released.

>

> It isn't recommended anymore because it wasn't very effective. Bud

> Offerman did one study where the bakeout lowered the VOC levels

> immediately, but his first post-bakeout sample, VOC levels jumped back

> up on the curve where they would have been, anyway. (so the reduction

> was very short-term). Currently, many recommend a " flush-out " with

> 100% outside air. I think it is more successful, and less expensive,

> since you're only paying for the fans, not heaters, but I have not seen

> any studies on flush-outs. Check the literature from the 1990's for

> more examples.

>

> So I have no idea if heating to 160 degrees would be successful at

> reducing formaldehyde or other VOCs, but heating to 90 degrees or so was

> not.

>

>

> Henry Slack

>

> As always, don't take my personal opinion above and construe it as my

> employer's (U.S. EPA) because it ain't necessarily so.

>

>

> <snip from Quack>

> I think that 160 degree heat would not be successful in extracting all

> the formaldehyde from fiberboard

> because isn't the fiberboard subjected to that level of heat in the

> factory already to dry it out? Its all

> incremental but the time factor is involved too. Still, heat would

> definitely help, perhaps enough to

> make it non-objectionable. Its a weapon in the arsenal, a good one.

>

>

>

>

> FAIR USE NOTICE:

>

> This site contains copyrighted material the use of which has not always been

specifically authorized by the copyright owner. We are making such material

available in our efforts to advance understanding of environmental, political,

human rights, economic, democracy, scientific, and social justice issues, etc.

We believe this constitutes a 'fair use' of any such copyrighted material as

provided for in section 107 of the US Copyright Law. In accordance with Title 17

U.S.C. Section 107, the material on this site is distributed without profit to

those who have expressed a prior interest in receiving the included information

for research and educational purposes. For more information go to:

http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted

material from this site for purposes of your own that go beyond 'fair use', you

must obtain permission from the copyright owner.

>