For beryllium work that involves unknown exposures and that has a potential for airborne exposure, respiratory protection shall be used until at least one of the following conditions is satisfied:

* Personal samples have been taken, and exposures for worst case conditions are known to be less than the AL.

* The work has been evaluated and compared to other, similar work in which exposures are known to be less than the AL.

* The work has been evaluated, compared to other, related work (in which exposures are known to be less than the AL), and determined to have less exposure potential.

All workers requiring or wanting to use respiratory protection shall follow the requirements of Document 11.1. Respiratory protection shall be chosen by the ES

Table 4. Required respiratory protection.

Exposurea

Required Respirator

<0.2 µg Be/m3

None

<2.0 µg Be/m3 (<10 x AL)

Half-mask, negative-pressure respirator with P100 filter

<10 µg Be/m3 (<50 x AL)

Full-face, negative-pressure respirator with P100 filter or half-mask PAPRb with P100 filter

<20 µg Be/m3 (<100 x AL)