There is no guarantee against unscrupulous inspectors clandestinely collecting samples and conducting off-site analysis to glean information on the chemical content of American products and the processes involved in making them.
For this off-site analysis, the Organisation for the Prohibition of Chemical Weapons (OPCW) - the implementing agency of the Chemical Weapons Convention - has established an international network of highly competent so-called "designated laboratories" that routinely undergo proficiency testing to ensure that their standard of analysis is up to the needs.