Methyl bromide is an odorless, colorless gas that is usually used as a fumigant for insect and rodent infected structures. It is as poisonous to humans as it is to other life forms. However, methyl bromide requires a much higher concentration in air and time of exposure to be toxic. A typical toxic dose of methyl bromide is about 10 times greater than a toxic dose of carbon monoxide and takes much longer to work. see Bromomethane in Wikipedia