How to cook with capsaicin and avoid chemically bombarding my housemates?
Essentially, don't let it heat/boil as much by itself. For example:


if it's a hot sauce that doesn't really need to cook with your stir fry, add after cooking, so it doesn't boil at all
add into a sauce, not by itself, so it's diluted
reduce heat or even remove the pan from the heat before adding anything spicy, so you can let it cook just enough, and not too hot/fast


That doesn't work if you have something hot that you need to cook with the rest the whole time (e.g. you want hot peppers in your stir fry), but since you mention stir fries with ground cayenne or liquid hot sauce, you have some flexibility. It's pretty common for stir fry sauces to only need really brief cooking at the end, enough to come up to temperature, stir to coat, possibly cook some corn starch through to thicken.