Yes. Anything from melting electrical components (eg. wires, capacitors, chips) thru "burning" dust to a dead animal could be the cause lol.
Open the case, run the computer and sniff around to try to isolate where the smell is coming from. Sometimes laying the tower on its side makes it easier to locate a smell's source. Then look at the part for any evidence of something visually amiss. And let us know what you find.
Use a pencil or something to stop fans from spinning when using the compressed air. This stops them from spinning too fast from the air hitting them. Also keep the can upright. You don't want the liquid in the can coming out on to components.
It is a preventative maintenance we should all doi on a regular basis. Computers are a natural haven for the elusive dust bunny. And that's one critter you don't want blocking or restricting air flow.
I've seen several mobos have their capacitors in the switching power supplies get hot and "tent". Capacitors have a safety feature to allow the cases to expand instead of blow up like the old parts used to. When they expand the liquid or paste electrolyte can leak out - smell is not pleasant. Look for bulges in the capacitors on the motherboard and also for signs of leakage.