Issue



IBM, others fail to understand vapor migration


04/01/2004







As founder and CEO of Clean Room Engineering, I spent over 30 years designing and installing hundreds of cleanrooms. Additionally, I lectured here and overseas on this and other related subject areas.

Also, I was called on to consult when serious contamination-control problems arose, having been involved from the beginning of the "clean" revolution of the late '50s to '60s. I found that my earlier experiences in fluid mechanics engineering and technology aided me in understanding and resolving contamination problems

Now to the chemical hazards issue. Early on, IBM and other semiconductor fabricators failed, and today still fail, to understand that positive pressure differentials could not and still will not deal with vapor migration principles. I frequently mentioned at my presentations that vapors will migrate against the directional air stream and similarly are not controlled by pressure differentials. Water vapor will move to equalize differences in relative humidity. Even positively pressurized facilities will allow vapor incursions of ambient outside air vapors/contaminants.

Solvents, bases and acids when attached to a water molecule will migrate in patterns totally ignoring air stream movement. Thus, workers in these environments are always subject to low levels—and sometimes much greater concentrations—of hazardous vapors. Then, the issue of capture and exhaust of "pure" solvent vapors will frequently depend on whether they are lighter or heavier than air, and lastly, the effects of the Brownian factor with regards to their dispersion routes.

Studies that I and other researchers made of fume hood type enclosures clearly showed that hoods designed to meet or exceed government standards easily allowed a portion of the vapors to travel along hand/arm entry points and reach operator breathing zones.

Short of using totally isolated enclosures, the exposure of workers to potential cancer-causing vapors/chemicals has rarely been properly addressed. I find it a sad note that with all the company and government good intentions, procedures, and regulations, the problems to this day are still serious and jeopardizing the health of a great portion of labor force. Unfortunately for our USA economy, maybe the outsourcing of this type of production will reduce future health problems here.

That IBM and others have escaped legal claims is a shame because they and manufacturers like them are truly guilty, but of ignorance and faulty engineering practices. I understand the pain and suffering of those who have been impacted with serious health problems and/or early deaths. It should never have had to occur, and it still places a black cloud over those industries that still fail to properly address exposure hazards.

Leon Hertzson

Founder and CEO
Clean Room Engineering
hertzson@optonline.net