I have a laptop that keeps getting dust in it and I have a complete diving equipment (tank regulator BCD ext.). Now normally you would blow out a laptop using a compressed air can and I was wondering if there is a safe(not like using a vacuum with all the risk of static electricity) way to use the scuba gear to blow the laptop clean?
While I wouldn't suggest using your expensive (and life critical!) SCUBA equipment for cleaning duty, if it's all you have, it'll work. Scuba tanks are often pressurized to several thousand PSI, which is a hundred times more pressure than you want for blow gun use. The regulators used in scuba diving bring this pressure down, often in two stages with two regulators. The mouthpiece often contains the second regulator.
The first stage regulator, closest to the tank (often on the tank) brings the pressure down to a usable range for cleaning items using a blow gun, though it's still higher pressure than most home/shop air compressors, so you'll want to be careful, or adjust this regulator to a lower pressure output. If you have no other tools or extra hoses, simply disconnect the output hose of the first stage from the second stage/mouthpiece. Turn the air tank valve to open and air will rush out the hose. Keep a firm grip on the hose when the valve is open, even at these moderate pressures, a whipping hose with metal connectors on the end can cause significant injury.
Many first stage regulators have limiters to prevent air loss in case of leaks, but it should permit enough air for cleaning purposes - just don't expect to be able to run air tools continuously from this without a more suitable high flow regulator.
Also, letting the air out of a scuba tank quickly in this manner may result in condensation inside the cylinder which may eventually damage the cylinder. It's really not a good use of life-critical SCUBA equipment, and particularly for high pressure cylinders. Make sure you inspect your tanks internally on a regular basis if you plan to use them for this purpose.
Needless to say, this is not a good idea. A SCUBA regulator is life safety equipment. It is designed to supply air to a diver underwater. Simply put, it keeps you alive. Using SCUBA equipment you intend to dive with in this fashion is highly inadvisable.
But let's ignore any personal safety concerns for right now. Could you do this, as you propose, without damaging the laptop in the process? Probably not. Your typical can of compressed air produces pinpoint blasts of air. A regulator second stage, on the other hand, is anything but pinpoint. It has a wide mouth to maximize flow rate. You could probably do it, but it wouldn't be very effective. It'd be only a little more effective than using your own lung power.
But the second stage regulator isn't the only way you can use a SCUBA regulator to deliver pressurized air. You also have the low pressure inflator line. XS Scuba manufactures a combination tire inflator/air nozzle that connects to a standard quick-disconnect hose. (You can find the catalog listing here). Let's say you were using that little gadget. Would you be able to safely clean your laptop then? Probably, but even this isn't ideal. From experience, a device like this shoots air considerably faster than a typical can of compressed air. You could regulate it to some degree by only opening the valve partway, though, so this could be a way to do it. You can also manually open the Schrader valve in the low pressure hose with a small screwdriver or something similar.
I am not even going to discuss methods that involve removing components of your regulator setup. If you are not a technician, do not take your regulator apart. Remember the part where you're working with life safety equipment? If you don't know what you're doing, don't take things apart.
I just cleaned my wireless keyboard with the leftover air in my scuba tank. I opened the valve (on the tank), held the keyboard directly in front of the airstream, and blasted away. I started at a low pressure and then gradually opened the valve until the air was coming out fast enough to depress the keys. It worked great, a lot of dust came out, and the air was free because the tank was done and I was going to take it back to the shop for a refill anyway.
I recommend using a spent tank (not a fresh tank that you plan to dive with) and starting out at a low pressure. To be on the safe side, you may want to lay a cushion on the ground in case you accidentally drop your keyboard. I was more worried about getting crumbs in the house, so I did it halfway outside in the doorway.
Hope this helps.