Wasn't sure where to put this, it's not really DIY, and it isn't "military", so here will have to do... I have done a webbysearchthing, but mostly found US stuff, and not many useful write-ups, just manufacturers sales pitches. The company I work for builds and maintains environmental monitoring equipment for mining companys, local government environmental agencies and so on. Many of the installations are in wells sunk into the ground or across small streams. One piece of kit that measures water quality, requires the sensor head to be cleaned at about 30 minute intervals with a blast compressed air. Currently, we use some awlful cheap crappy ones which were chosen due to time constraints and price. They are failing left, right and centre... The requirements we have are: Air pressure upto 6 bar Supply voltage 24 VDC Working temp as low as -30 °C Smallish - the ones we use are about 350 mm x 250 mm x 150 mm. Ideally available in Europe. The are in a enclosure, which will shelter them from the worst of the elements like rain, snow, direct sunshine and so on, but they will be subject to damp air, creepy-crawlies and other niceties of outdoor life. We use a system where an air reserviour is filled to about 6 bar - though we had to drop it to 5 - 5,5 bar because the current compressors can't handle it. This is controlled by a pressure-sensitive switch. When the air pressure in the reserviour drops to 4 bar (now 3 to 3,5), a relay opens and turns the compressor on. With regards to price, cheaper is nice, but since the value of gear in at the staitions can be in range of tens-of-thousands of Euros, a few extra hundred or so isn't going to make that much of a dent. The cleaning takes place every half hour, which means the air bottle needs topping up every couple of hours or so. Has anyone had any long term experience with anything suitable? Cheers!