This is a very rare occurrence in many cities the world over due to the pollution we have from cars and the many industrial plants that may bring more than the normal pollution sources. There is however a lot of products that can not only filter air but kill viruses and bacteria that used to cause the musky smell of old air conditioning units. Old AC units, get them cleaned frequently so they stay efficient and eat less electricity.
Get hold of some after-market filters that trap better than the original built-in filters, some form 3M are dipped in special anti-bacterial solutions that kills contaminants and have better filtering abilities. Space filters that act like large vacuum cleaners are also available and they normally come with activated carbon filters that gets odors out of the contaminated air of such and enclosed space as a condo.