Search for "`chemical name` msds". You may need to look for the specific chemical name [1] rather than trade name. You should be able to find an occupational s

Search for "`chemical name` msds". You may need to look for the specific chemical name [1] rather than trade name. You should be able to find an occupational safety limit, lower exposure limit, or similarly worded section, which tells you how much (roughly) you can be safely (roughly) exposed to per unit time, usually 8 hour workday. Anything that isn't air doesn't belong in your lungs. Period. Some things are less bad than others. However diffusers are unlikely to increase the concentration to harmful levels for healthy individuals. As an asthmatic though, I can definitely feel it when lots of diffusers are running. [1] http://www.chemspider.com/ http://www.chemspider.com/