Although likely not the first to do so, he prepared and inhaled nitrous oxide to prove that it didn't cause disease, and thus discovered its respiratory effects, but later nearly died from inhaling water gas.  
Although likely not the first to do so, he prepared and inhaled nitrous oxide to prove that it didn't cause disease, and thus discovered its respiratory effects, but later nearly died from inhaling water gas.  Later, he conducted work on electrolysis, laying the foundation for the modern electrochemical series, leading to his discoveries of sodium, potassium, barium, and calcium. Mentor to Michael Faraday,  FTP, name this 19th century British scientist, exponent of the scientific method and inventor of the miner's safety lamp.
Although likely not the first to do so, he prepared and inhaled nitrous oxide to prove that it didn't cause disease, and thus discovered its respiratory effects, but later nearly died from inhaling water gas.  
Sir Humphry Davy