The smell of spray paint but no causes?

Sometimes when I come home I smell spray paint. I live in a apartment but there is nobody painting. The smell is only there sometimes and sometimes I am the only one that smells it. It is starting to worry me. I know my water heater is making noises like there is water running that I have never heard before. I dont know any suggestions would help.The smell of spray paint but no causes?
You didn't tell me about the water heater.... that could be the problem due to build up of lime and calcium or a gas leak..... have it checked! another possibility someone huffing in an apt close to yours but definitely have the water heater checked . Just call maintenance and put in an order.