Practical info: How are grains sterilised before being sold

It is well known that grains ought to be sterilised before being sold otherwise they create a media that is conducive for the proliferation of insects.  According to one shop owner who sells grains, Ahmed Halbawi, sterilisation is done by using a chemical licensed by the Ministry of Health.  Halbawi added that this chemical consists of a smoke inducing matter in the form of pills and it is placed within the grains in a closed and refrigerated room, where it is left to interact with the grains during a period of 36 hours before its smoke subsides.  After then, odors are sucked out with a special instrument, and the door to the room is opened in ten centimeters width before being completely open.  Whoever enters the room should be wearing sterilised outfit which also serves as protection for those who suffer any form of allergy.
Source: Al-Safir 26 November 2014