You probably use chemicals frequently, because many electrical jobs involve the use of them. For example, you may use solvents, epoxies, and lubricants to install a motor. Chemical hazards range from mere irritants to very potent substances. Chemicals can cause two types of hazard: physical and health. What's the difference between the two?
A physical hazard is where a chemical reaction could harm you. Such a hazard may involve flammables (e.g., hexane), reactives (e.g., sulfuric acid), or both. A health hazard is present where chemical contact or ingestion leads to illness or injury that is latent (occurs later, as with carcinogens like trichloroethane, aka, "safety solvent") or chronic (you develop a condition such as bronchitis).
You may not immediately notice the effects of a given chemical and thus assume it's safe to use without special precautions. This assumption can mean health hazards that morph into painful, disabling health problems in the near future. Don't assume. Follow directions provided on labels and MSDS.