mike on 2017/01/26 wrote:

I think you're confusing compressed air with a phase-change
propellant. You can't get enough compressed air into a "duster" can
to do anything useful. You can use air pressure to dispense a small
percentage volume of payload, like paint, but the pressure varies
considerably as you use it up. The downside is that phase change
propellants useful at human temperatures and spray can pressures have
side effects, like flammability or ozone depletion or toxicity.

Correct, there is no air (nitrogen+oygen) in a typical duster can. They
contain difluoroethene, trifluoroethene, or tetrafluoroethene. They are
considered as "greenhouse gases" (if you believe that humans are
responsible instead of, increased gamma radiation from the sun that
generates more cloud cover - but the sun cannot be taxed as can humans).
Tetrafluoroethene (HFC-134a) has been replaced with less expensive HFCs.
Those that use butane or other hydrocarbons were abandoned years ago
(decades maybe) because of their flammability.

I just checked those that I recently bought at the hardware store. They
note on their label "Bitterant added". That means they use an HFC as
the propellant. Luckily the one that I got has an MSDS (manufacturer
safety data sheet) available online. No, they don't give the URL on the
can but I found it via searching "msds ultra duster". It's at:

http://ultraduster.com/msds.html

As can be read there, it uses difluoroethene. I found another that I've
used at:

https://www.google.com/url?sa=t&rct=...B4jQxA&cad=rja

It also uses difluoroethene. You can also buy dusters that attach to a
CO2 (carbon dioxide) cartridge. You can buy tanks of air, oxygen,
nitrogen, or whatever you want and hose off from the tank but you'll
need a regulator at the end to lower the pressure.

There ARE true air duster cans. They only contain air and as such have
much shorter "run" times. You get about 10 times the volume of the can
for the compressed air but as with any propellant the pressure goes down
as the volume decreases (non-linearly, of course). The compressed *air*
cans that I got from a buddy at Medtronic were normally reused by
attaching them to a compressor (with filters for purity). I didn't have
the compressor and my buddy there moved away so there was no way to get
the cans refilled. They had a micro-adjustable trigger that let you
adjust the air flow to miniscule to full blast. Those did use AIR.