Most commonly used solvent vapors have “Permissible Exposure Limits” (PELs) or allowable amounts in the air. Most of these limits are based on average 8-hour exposures – a few are peak or ceiling limits. The lower the limit, the more toxic the solvent is. Examples of PELs for common solvents:
ppm = parts per million 10,000 ppm = 1% in air
Many of these chemicals are no longer used because of their high health hazards. However, they may occasionally show up in products in small amounts, in products from other countries, or as an unintended contaminant.