> I now carry a spray that puts bacteria in the air that displace other bacteria and no colds and coughs anymore. But that's not mainstream.

No, it's not, I've never heard of it! I'm pretty skeptical of new medical claims, though, and I'm curious about this description. From my limited understanding, don't think the bacteria in air are like a bathtub full of objects that take up space, or like an ecosystem that compete for resources and reach an equilibrium: it's more like an ocean full of fish, where spraying more fish into the water aren't going to do much about the existing sharks. Can you provide a link or description of this product?

> There's probably a lot of sick people out there, thanks to AC.

This is also a claim I find surprising. Air conditioners are ubiquitous around here in the summer, but I've never heard of a health risk from them. I'm aware that the cheap window units can develop condensation puddles if improperly installed (I cleaned one out in my old apartment that was disgusting), but the typical business has central air and I thought it actually improved the microbial situation by dehumidifying the air. Citations for this claim?

I get what you are saying and I'm not anywhere near as informed as you are. Although I did see some lab tests that did show a change in the bacterial environment after using the spray and the fact that it works for me, personally. I spray some in my car and bedroom as well.

I cant give a name though; I just bought a box of 'samples' from a guy that's doing some research with it. But it's years away from market, judging from his story. Could send you a 20ml spray if you'd like. :)

As to your 2nd point, go find your indoor blower(furnace closet for split system or outside in a package unit), pull the power supply, then open and take a look inside at the blower wheel. Unless the unit is a less than a year old you will will clearly observe why health risks do exist. If you need more proof see the evap coil & the primordial sludge in the condensate tray/drain. When finished, reassemble, plug power back in & change your air filter.

I clean out my evap coils and condenser coils annually, and replace my filter twice a year (for efficiency, not for health). I'm well aware of the dust that my filter removes, which makes my indoor air cleaner than outdoor air. My allergen-sensitive wife proves experimentally that it has a strong positive effect for a couple weeks every spring and fall. And I'm aware of the crud that develops in the condensate tray. There's little crud in my central air system, but when I used a window AC in an apartment and the unit wasn't leveled properly it got pretty bad.

More generally, though, the presence of unattractive substances does not imply a health risk. My yard is, in the most basic sense, an enormous pile of dust, plus a few organics that grow and decay into dust. My home happens to be a few hundred meters from a lovely trout stream, and that stream and its floodplain contain more life from bacteria to algae to fish than any primordial sludge ever had. Neither are dangerous.

Legionnaire's disease thrives in air conditioners https://en.wikipedia.org/wiki/Legionnaires%27_disease

There's little risk of disease (Specifically, Legionnaires') from residential air-cooled A/C systems. The risk is typically from industrial air conditioning systems which use a water-based heat exchanger between a radiator system on the roof and the condenser. The water in this system is kept warm. The water in the condensate tray of a typical AC is cold and continually drained, so the disease doesn't propagate well.

The common cold is caused by a virus, not by bacteria. You can get the bacteria that cause Legionnaire's disease building up in the fluid in air conditioning units and then getting vaporized into the air, but I don't see how spraying more bacteria around is going to stop you from breathing in the ones the AC is blowing into your face.

I'd be very curious about which bacteria you have in your spray, and which bacteria they're supposed to be displacing.

That's a problem with your AC unit's poor antibacterial filtration and your home's filters. Filters should be replaced every few months, if not monthly. There's also UV lamps that can be installed in AC's, or units that come with them, to sterilize the coil and air.