Testing the odorant content of natural gases. Natural gas is by nature odorless and for safety reasons it must be provided with an odorous substance (odorants tetrahydrothiophene or tertiary butyl-mercaptan). In Germany the odorant content of natural gases has to be tested regularly in accordance with DVGW regulation G 280/281. The EX-TEC OD 4 is the ideal measuring device for odorant measuring by the gas supplier.