The method by which insect pests are exposed to fumes of chemical without contaminating the stored food grain is called

The method by which insect pests are exposed to fumes of a chemical without contaminating the stored food grain is called fumigation.

Here are the steps involved in this process:

1. Identification: The first step is to identify the type of pest that is infesting the stored grain. This is important because different pests may require different types of fumigants.

2. Selection of Fumigant: Once the pest is identified, the appropriate fumigant is selected. The choice of fumigant depends on the type of pest, the temperature and humidity conditions, and the type of grain being stored.

3. Application: The fumigant is then applied to the stored grain. This is usually done by placing the fumigant in the storage area and allowing it to vaporize. The fumes penetrate the grain and kill the pests.

4. Aeration: After the fumigation process, the storage area is ventilated to remove any remaining fumigant. This ensures that the grain is not contaminated with the chemical.

5. Monitoring: The final step is to monitor the stored grain to ensure that the fumigation was successful and that no new infestations occur.

This method is effective because it can control pests without contaminating the grain with chemical residues. However, it should be carried out by trained professionals to ensure safety.