Have you ever had one of those days when you walked into a communal restroom ready to relieve yourself, you found that someone is occupying one of the privacy stalls, and then all of the sudden you get that burning sensation that every aveoli in your lungs is systematically being destroyed by the stench that preoccupied said restroom?  And I'm NOT referring to that natural methane by-product produced by humankind (I'm not that juvenile).  I'm referring to the manmade aerosol chemicals crammed in a pressurized metal enclosed container.  I sometimes find that I'd rather bath in the gaseous by-products of the Mexican bean soup that you had last night instead of having my sinuses and lungs being eradicated by acidic fumes created in a guise of a family household product.

Maybe we need to install better exhaust fans in our restrooms.  Or maybe we need to eat more foods that create less gaseous waste.  But some of these air "fresheners" wil eat your insides alive.

Does NO ONE uses the bathroom anymore these days...? :p

Lol, I feel ya, bruh. My gf and I uses mostly nature friendly deodorizers. We like the scentsy products. The last purchase we bought are these things from the shopping channel, Poop-pourri.

As far as your title, it's hard to choose. Biological is the way to go, I think. I may have read somewhere that it can be target-specific like DNA.

Although, chemical could produce zombies...

My grandfather, a biology professor has a little private theory that the plastecizers we put into anything from cleaning producs, over shower gel to hand soap are actually responsible for the majority of the so-called lifestyle-deseases. They are known to cause cancer and confuse the hormonal balance and he thinks they might also be the source of a lot of allergies and such.

So you're not alone in thinking, that innocent little hosehold producs are potentially dangerous. Even though I've never heard him talking about the smell in particular. :P