To more fully understand how threshold limit value (TLV) relates to the work you're doing, here are some examples of where various industrial chemicals fit on the spectrum:

  • TLV of 1,000 ppm or higher: Very low toxicity. Examples: acetone and Freon.
  • TLV of 500 to 1,000 ppm: Mild toxicity. The spray lacquers you use for enclosure touchup are examples.
  • TLV of 1 to 500 ppm: Moderate toxicity. The alcohol you use to clean electrical contacts is an example at the upper end of the range. Halo-generated solvents cluster at the lower end. Ketones fall in about the middle (Methylethylketone TLV is 200).
  • TLV less than 1 ppm: Extreme toxicity. While you are unlikely to use them directly, you may encounter dimethyl acetamide or methyl acrylate as process chemicals, especially in fiber-related processes. If you work in a Class III Hazardous location, there's a good chance these chemicals will also be present.