The individual airlines may post their policies in their Conditions of Carriage or some such document.
Southwest Airlines seems to refer travelers to the TSA rules, but additionally prohibits self-defense sprays.
Carryon Baggage
While Southwest doesn't talk about inflatable life vests, it does prohibit cartridges for inflating life rafts:
Life Raft Cartridges associated with a self-inflating life raft must be removed and are not allowed on Southwest.
https://www.southwest.com/html/customer-service/baggage/special-luggage-pol.html#baggage_special_luggage_pol_tab_list_tab_12
FAA brochure...
http://www.faa.gov/about/office_org/headquarters_offices/ash/ash_programs/hazmat/media/materialscarriedbypassengersandcrew.pdf
Note the wording
"with the approval of the aircraft operator"
Southwest Airlines seems to refer travelers to the TSA rules, but additionally prohibits self-defense sprays.
Carryon Baggage
While Southwest doesn't talk about inflatable life vests, it does prohibit cartridges for inflating life rafts:
Life Raft Cartridges associated with a self-inflating life raft must be removed and are not allowed on Southwest.
https://www.southwest.com/html/customer-service/baggage/special-luggage-pol.html#baggage_special_luggage_pol_tab_list_tab_12
FAA brochure...
http://www.faa.gov/about/office_org/headquarters_offices/ash/ash_programs/hazmat/media/materialscarriedbypassengersandcrew.pdf
Note the wording
"with the approval of the aircraft operator"
