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Thought about blasting my LT150 while it's on to see if it'll rid of a dust blob but worrried about flamability mentioned on can. So blasted some air towards a candle and it's like a BLOW torch !!!. Good thing I didn't try with LT150 as it's pretty darn hot while running due to hot lamp.
 

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Huey,


That subject was scary! I expected to find a disaster story in here.


I'm glad that you and your equipment are safe.
 

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Huey,


I've safely blasted canned air into my VT540, But I did it within 2-3 minutes after start up. Didn't cause any problems but didn't help anything either. Still have the dust blob smack in the middle of my picture:mad:


Jayson
 

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Wow what are you guys over there putting in your canned air??

AFAIK canned air is compressed nitrogen which if my chemisitry from UNI days serves me correctly doesn't burn that well (like not below fusion temperatures :) ). Is it specifically canned air or some other type of similar spray Huey? I don't mean to imply you are incorrect ( or shouldn't trust your own eyes :) ) I just wondered if what you used was more than cleaning compressed air as it sounds like you definitly have a hydrocarbon present for it to burn like you describe?


Regards


JohnP
 

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Well I was dumber than most, about 2 years ago I use the canned air w/pj running........ and WOW it started on fire, but it only burnt off some of the bulbs mirrored surface, it flaked off and floated in the air, it actually. floated up as if it were lighter than air. It looked like silver gliter, but the bulb still worked and I couldn't tell any difference in the PQ . I was lucky I wasen't injured.
 

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You should never use canned air or compressed air on a warm projector! The canned air exits the nozzle at low temperature like freon and when it comes in contact with a warm dichroic or firstsurface mirror the surface will become crazed (small hairline cracks). This is a very expensive part to replace.
 

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Yeah, not all canned "air" bears any resemblance to air (except maybe in LA ;)). Some of them are flammable, as Huey noticed (good for you for reading the can!!)


ghbliss raises a great point, too. Dust 'em while they're cold, and be careful not to get the nozzle or the little tube too close to the parts of the projector, as you may end up forming frost on them.
 

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"Canned air" is not just air - it needs a propellant - a liquid with a low vapor pressure.


Some of the liquid vaporizes in the can, until the pressure equals the vapor pressure of the liquid. Then the vaporization stops - and you have a 2-phase mixture in the can, plus the air, hair spray

or whatever. When you press the valve on top, you open the path for the pressure to drive the contents

out. This also lowers the pressure and allows more of the liquid to vaporize to generate more pressure

to expel the contents - until you close the valve and establish equilibrium again.


Aerosal cans originally used Freon, the stuff that is in air conditioners. It had the desired vapor

pressure properties, and was basically inert and non-flammable.


However, then came the concern about the "ozone-hole" and Freon in cans was banned.


Aerosal cans now use propane and other flammable propellants.


For safety's sake, keep ALL aerosal cans away from flame or hot surfaces that could ignite the flammable

propellant!!!


Dr. Gregory Greenman

Physicist
 
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