Canned Air in Your Car's AC?

Don't do it.
Canned air is usually R-152a. You're not spraying air. You're spraying refrigerant. This is the reason some people may be tempted to use it in their car's AC system.

Again, don't do it. With that out of the way, let me explain why.

• It's illegal to vent any class I or class II refrigerant in the list on 40 CFR part 82 subpart A, appendix A & B. Although canned air does not fall under these categories and is not ozone depleting, it does impact the environment due to its fluorine content. 
• If you put any refrigerant other than R-134a into your AC system, you will have a hard time finding an AC repair facility that will service your system. They don't want to contaminate their recovered refrigerant. And they don't want to vent your refrigerant. 
• The impurities may damage your AC system. Canned air has bitterants added. I don't know how this will react with the PAG oil, but again, this contaminates the AC system. When sold as canned air, it is exempt from the contamination requirements for refrigerant, such as air, moisture, and particulates. You don't know what you're getting. 
• R-152a will not get as cold as R-134a at the same pressures. It's close, but won't be as good.
• Canned air is close to the same price as R-134a, so why not do it correctly?
• Canned air R-152a is highly flammable, with a flash point of colder than -50C. The combustion by-products are seriously toxic. You don't want it in your car's AC. It could easily ignite in an accident, producing highly toxic fumes. Although it is approved for use in new systems, you are not allowed to use it in systems not designed for it. 
• Flammable refrigerants are illegal for use in motor vehicle air conditioners. Well, except for R-152a and R-1234yf. Why? Because inconsistency. 

Here's a quick comparison table. Canned air uses R-152a. But canned air can't be regarded as the same quality as R-152a refrigerant. 

	R-134a	R-152a	R-600a	R-1234yf
Auto-ignition temperature	750ºC	454ºC	460ºC	405ºC
Flash-point	250ºC	<-50ºC	-83ºC	Not available
Global warming potential (GWP)	1300	138	3	1
Ozone depletion potential (ODP)	0	0	0	0
Cost / kg	$14.70	$13.95 (as a 12 pack of 10 oz cans)	$26.45	$220.46
Combustion by-products	HF, COF2	HF, COF2, CF4	CO2, H2O	HF, COF2
Boiling point at 100 kPa	-26.3ºC	-24.7ºC	-11.7ºC	-30ºC
Chemical formula	C2H2F4	C2H4F2	C4H10	C3H2F4
Atmospheric decomposition	TFA	CH3CF2OOH, COF2		TFA
Toxicity AEL (ppm)	*1000	*1000	*1000	500
IDLH (ppm, 30 min)	50,000	12,000	Simple asphyxiant	16,000
Atmospheric lifetime (years)	14	1.4	12	0.03
0ºC PSI	28	23	8	31
60ºC PSI	229	203	111	223