More About Threshold Limit Values

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.