Negative pressure for contamination containment

[maddend]

Is there a maximum acceptable differential pressure between spaces before special precautions need to be taken for personnel?
With pressure fluctuations between spaces for transient conditions like door openings the rooms can fluctuate between -0.02 to -2.75 inches of water.
Having been exposed to air locks at BWR nuclear plants I remember 12 psi absolute in the building and being able to enter it with no special depressurization adjustment time, is this still acceptable? Personally I am not worried about a delta p of 2.75 inches of water but I don't want to overstep an OSHA restriction.

 

[chicopee]

It all depends on the type and level of contaminant(s) and the amount of oxygen within the space you want the negative pressure. OSHA states 19.5% oxygen in confined spaces as long as there are no contaminants and the ambient pressure is atmospheric; however this 19.5% means that an inert gas such as nitrogen has displaced the oxygen level from about 21% to 19.5%. The level 19.5% represents an oxygen partial pressure in the alveolar spaces of the lungs of about 98 mmhg which is the minimum level of oxygen that you want in the negative containment. To have the minimum level of 98mmhg in the alveolar spaces, a reduced ambient pressure of 13.6 psia of dry air, or if humidity level is around 50% increase the 13.6 psia by about 0.1% for the contaiment pressure; assumption is atmospheric pressure at 14.69psia.

 

[chicopee]

The number that you quoted of 12 psia at the nuclear power equal 620.8 mmHg which with a regular air having a concentration of 21% oxygen, the partial pressure of oxygen would be 130.4 mmhg and subtracting 50mmhg, you would have an oxygen partial pressure of 80mmhg in the alveolar spaces. The physiological response would not noticeable to this reduction but if the oxygen level was 19.5% then the alveolar space would have an oxygen partial pressure of 71 mmhg then the physiological response would be impaired thinking and reduced coordination.