I think some people are confusing containment issues with sample prep issues. I fully agree with those that have compared containment of nonoparticles to containment of gas molecules. A properly designed fume hood should contain both quite nicely. The problem with hoods designed to operate in the 80 - 100 fpm range is that you may lose most of your sample if it is dry and outside of a matrix. The problem with low flow hoods is that they become ineffective when the environment creates challenges (open doors and windows, poorly designed air supply systems, poorly trained operators, cooling fans, etc.) that overpower the finely tuned capture capabilities of the hood. The proper containment device for dry nanoparticles may not be a fume hood at all but rather some form of glove box -- not unlike working with friable asbestos in a glove bag.

Al

On Wed, Aug 5, 2015 at 1:16 PM, David C. Finster <dfinster**At_Symbol_Here**wittenberg.edu> wrote:

Debbie, and others,

This makes (some) sense to me; I understand that nanoparticles that are not in some matrix are prone to easy dispersal. What puzzles me is: if these tiny particles can "blow around" easily, surely they don't "blow around" more easily than some gas (NO2, H2S, etc) - do they? Could they? Seems to me that tiny molecules and tiny nanoparticles would behave about the same in this regard. Thus, if a "high" flow rate of 100 fpm is inappropriate for nanoparticles due to "excess turbulence" (I'd guess) then why would this not also apply to "regular" gases?

If we empirically KNOW that the lower flow rate for nanoparticles is appropriate then this a good guideline, of course. It just doesn't make intuitive sense to me.

Dave

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