ISO 20492:2008 establishes two methods for testing the resistance to fogging of pre-assembled, permanently sealed insulating glass units or insulating glass units with capillary tubes intentionally left open. The two methods are designated as approach 1 for markets such as North America, and approach 2 for markets such as Europe.

ISO 20492:2008 is not applicable to sealed, insulating glass units containing a spandrel glass coating due to testing limitations.

ISO 20492:2008 does not apply to insulating glass (IG) units whose function is decorative only.