A gas dryer uses the available air in the room to burn the gas when it heats. If there has been any recent painting or floor sealing done within 200 yards of the dryer, it will pick up the petroleum distillates in the paint fumes and combust these along with the rest of the air. Sometimes this makes the clothes smell funny, as though there were a gas leak or something burning. Even though the fumes themselves might not be detectable by the human nose, they are still present on a molecular level and will cause this issue.
There is nothing you can do to resolve this until the sealer finally cures in the area, taking several months sometimes. You can help mask the odor to some extent by using Bounce sheets in the dryer. This is a phenomenon peculiar to gas dryers only, not electric.
The fact that the floor sealing was done upstairs does not matter, as it shares the same air with the basement. You can expedite the situation by airing out the affected room upstairs so that the fumes dissipate faster. (summer heat may preclude this)