A schoolmate and close neighbor live in a house that requires A/C for it to be comfortable, but this means that she has to have the A/C and heating system running when it is summer time and winter, respectively… She depends on the Heating and A/C system actually to survive.
This one time, she felt some unusual plastic smell from her heating system, but it had been a long time before it was used since we had just come from a long summer time season. It is possible for one to feel the burning smell after a while of heating system disuse. Typically, this results from accumulated dust and dirt, which must burn first before the heating system can heat up. It should take a few minutes before the burning smell dissipates! However, when the scent tends towards plastic, then you have to be cautious. This could mean multiple things, with the first being that some plastic material may have been accidentally left inside the heating system and is now burning when you light it. It is also possible that wires could be burning or worn out and in need of repairs. The latter case is the most proper occurrence, and components that need to be substituted in this case include capacitors that are often plastic coated and will smell burnt plastic when they malfunction… Others that could lead to this smell also have the fan belt and plastic-coated wires, when these components wear out, they are actually affected by heat and, as a result, will burn. In her case, the pieces were worn out and needed urgent substitutement. However, consistently call an Heating and A/C corporation to assess the detriment and advise otherwise. If the smell intensifies with time despite switching off the heating system, you need to contact the fire maintenance to be on standby just in case something serious happens.