All air measurement devices and methods, including expensive EPA approved SUMMA canisters and laser methods are just estimates. The EPA admits that they have no solution for the fact that chemicals in the SUMMA canister can and do react and decompose after the measurements are taken. And even with expensive devices that cost hundreds of thousands of dollars or even millions of dollars there is no proof that they are accurate or “right.” Any device or measurement of air samples should be considered an estimate only. These TVOC meters are useful for seeing if you have some mystery exposure in the middle of the night, for example, then you can run more tests. Beyond that you should always try to get the lowest reading possible. In reality the chemicals in the air are constantly changing, combining, decomposing, and reacting at random. The EPA published guides on most hazardous chemicals and the German FEA publishes a TVOC levels chart. OSHA limits and recommendations do not apply to residential situations, only to workplaces, so you should use EPA and other guidelines for residences. If you have a serious concern about the chemical exposure indicated by a TVOC monitor you should contact someone like Fike Analytical and take a snapshot while the TVOC or particulate is elevated. Then you can know more accurately what’s in the TVOC and how dangerous it is. This isn’t medical advice.