Oh! Here’s a niche one, but:
-pepper spray/OC is an oil based capsaicin spray, you need lots of soap and water to remove it, and it’s persistent, it will stay on your clothes and skin until removed by chemical means. You can make homemade Sudecon wipes by blending 60% water, 30% sugar, 10% unscented baby shampoo, and 0.5% powdered citric acid, then soak disposable shop towels in it. That’s the same stuff the police and military use to remove the chemicals when they accidentally get themselves with it, or that paramedics or ER nurses would use.
-tear gas/CS is a chemical irritant powder that you breathe in and then it also sits on your skin and is activated by water, including sweat. This means that it’ll reactivate later when you least expect it, and transfer in the meantime without your realizing it. There’s not much to do other than wipe your skin with the Sudecon and then get showered as soon as possible. In the field the best approach is to just get hit with a hose from head to toe.
In no situation is milk the correct answer to either of these, despite a lot of bad advice to use it because people think the fat will help wash away the pepper spray. It’s no more useful than water and less useful than soap and water, and ineffective against CS. It will also give a person eye, nose, and ear infections and they’ll smell like hell and be out of the game for the day, vs just being wet and able to dry off.
If you want to wash someone’s eyes out from exposure to either of these chemicals, you need a bike bottle or similar squeezable water bottle with a strong tight stream. Have the person kneel and sit on their hands (keeps them from slapping the bottle away). Stand over them facing each other and have them tilt their head up looking vertically at you, take the outside of your thumb and roll their eyelid up from the nose side of it and spray with the other hand across the eye from the tear duct outward toward the ear. We’re basically doing a high-pressure version of what your tear ducts do, sheeting a clean solution over the eyeball to drain out the corner. This lifts and moves the chemicals off rather than driving them farther into the socket like if you sprayed straight at the eye perpendicularly. Do that a few times on each side and then see how they’re doing. Their vision should come back after a round or two, depending on how much of a hit they took and whether it was civilian or military grade. Wear gloves while doing this or wash your hands right afterwards, there will be transfer from their face to your hands. Also make sure they wash their hands before they touch their face or they’ll recontaminate since everyone gets hit and then rubs it into their faces trying to get it off, which means their chest and hands are the main sites of possible recontamination. Some people have respiratory issues afterwards, that can be either throat and lung mucosal membrane irritation or just panic causing hyperventilation and gasping/choking. Either way, it’s a thing to monitor. Also, you need to identify yourself and ask permission to help before trying these things. Someone who’s just been hit with chemical weapons is just as likely to run or hit you as understand that you’re trying to help.
In advance: no asking me how I learned these things, if you weren’t there you don’t need to know.