In room temperature (25 deg celcius), on regular walls and floors such as laminate and bathroom tile. In this case an insect poison compound would've been sprayed on these surfaces, containing acetamiprid 0,005 %.
My definition for "fully decomposed" is the state where no acetamiprid is left whatsoever (or the amount is next to nonexistent) as it decomposes over time naturally.
With harmless I refer to humans and pets.
With measure of harm on the other hand I refer to a state where a certain amount of the chemical would cause no harmful health effect in any way.