Atmos, or The Air is On Fire.

[Clarks]

Can you add chemical reagents? Can I use the scrubber to spread bathsalts all across medbay?

Basically I'm curious to how to interact with these I guess.

Atmos only works with gases, not reagents. The scrubber is not meant to be a fog machine.

The scrubber makes air circulate. Inside there are a number of slots where you place cartridges that act like switches for certain gases.
Instead of having a large tank full of plasma, one of O2, CO2 and N2O, like old atmos, each scrubber can transform a gas into another when a cartridge is inserted.
When the correct cartridge is added, the scrubber will delete some O2 from the air it circulates, and add plasma in its place, or CO2.
Cartridges may contain chemicals, but they are not like a beaker. It's partly to make hacking atmos more challenging than flipping two switches, and partly for the sake of realism (rebreathers work more or less like this).