Has air sampling for equivalent or more potent compounds been performed to verify the performance of the hoods, significantly above a standard hood face velocity measurement?
If it has, then a respirator is NOT required.
If personal breathing zone samples have not been collected and the only performance verification of the fume hoods is face velocity measurements, then I would recommend respiratory protection until a potential exposure has been disproven.. I've found hoods that have actually been exhausting contaminated air back INTO a laboratory (the architect said it was impossible, but concurred after observing smoke generated from a theatrical generator inside of the hood push the fog back into the lab). Additionally, I have validated lower flow rate ventilated balance safety enclosures controlling particulate emissions from potent pharmaceutical compounds measurements that have a much lower occupational exposure limit. Lead acetate has a TLV-TWA of 0.05 mg cu m as Lead, and inorganic compounds, as Pb.
Defining zero anymore is problematic, in the early days if we could measure at a low ppm level, we thought we were doing great. Technology now allows us to quantify exposure levels at the nano- or pico- gram levels, amazing! The key is to know the difference between quantification level vs. occupational hazard level - that is what drives the controls.
Verify and/or measure and let the exposure results drive the respiratory protection requirement.
My opinion only,
Need an expert opinion here. One of my faculty was told by someone that she needs to use a full facepiece respirator to work with lead acetate. I definitely understand the risks associated with lead, especially as a powder. However, I am very confident in our hood function and her using the hood properly. If she is doing her weighing in the hood, would lead acetate still warrant the use of a respirator? Or, would I have to prove that we are keeping the exposure limits to zero to have her not use one?
Sigma's SDS Info on the compound:
A system of local and/or general exhaust is recommended to keep employee exposures below the Airborne Exposure Limits. Local exhaust ventilation is generally preferred because it can control the emissions of the contaminant at its source, preventing dispersion of it into the general work area. Please refer to the ACGIH document, Industrial Ventilation, A Manual of Recommended Practices, most recent edition, for details.
Personal Respirators (NIOSH Approved):
If the exposure limit is exceeded, a half-face high efficiency dust/mist respirator may be worn for up to ten times the exposure limit or the maximum use concentration specified by the appropriate regulatory agency or respirator supplier, whichever is lowest. A full-face piece high efficiency dust/mist respirator may be worn up to 50 times the exposure limit, or the maximum use concentration specified by the appropriate regulatory agency or respirator supplier, whichever is lowest. For emergencies or instances where the exposure levels are not known, use a full-facepiece positive-pressure, air-supplied respirator. WARNING: Air-purifying respirators do not protect workers in oxygen-deficient atmospheres.
Thank you for all of your wisdom.
Monique Wilhelm, M.S., NRCC Certified CHO
ACS D-CHAS Secretary-Elect|2017 CERM E. Ann Nalley Award Recipient
Laboratory Manager|Adjunct Lecturer|Chemistry Club Advisor
Department of Chemistry & Biochemistry|University of Michigan-Flint
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