What is this yellow powder under my carpet?
Looks like degraded carpet glue.
Asbestos seems highly unlikely, but you can have it lab tested if you have asbestos-paranoia. If the house is less than 35-40 years old, it's exceedingly unlikely to have any asbestos anywhere. If it's older, it becomes more likely.
The &quot;classic&quot; asbestos-containing floor adhesive is &quot;black mastic&quot;