Approved Document D relates to the use of cavity wall insulation and it’s potential to release toxic fumes into the building.
Any materials which could give off fumes should not penetrate occupied parts of the building. Such material may only be used where there is a continuous barrier which will prevent fumes from entering any occupied areas.
Part D stipulates the conditions where such materials can be used and the minimum standards which need to be applied.
Approved Document D – Requirement
D1: If insulating material is inserted into a cavity in a cavity wall reasonable precautions shall be taken to prevent the subsequent permeation of any toxic fumes from the material into any part of the building occupied by people.