Hello Volatile chemicals like formic and thymol can be much more hazardous to the operator than an organo-phosphate like coumaphos. The LD50 attempts to rate all substances on the toxicity if ingested. This is a gross oversimplification at best. No one would be likely to ingest a Checkmite strip, but one could easily inhale fumes from formic or thymol. I have handled all these substances and I regard Checkmite as very safe to the operator (provided nitrile gloves are worn). The others, as well as the old demon Phenol, are risky and should be used with caution and plenty of fresh air. Isis Glass Ann Arbor, MI USA :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -- Visit www.honeybeeworld.com/BEE-L for rules, FAQ and other info --- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::