A spray gun, used to apply paint, uses Bernoulli's principle to function. It contains two tubes inside of it: one tube comes up from the supply of paint and one supplies a flow of compressed air that blows across the top of the paint tube. This rush of air creates , which sucks the paint up the tube and into the stream of air.

Low pressure

Explanation:

Take two nearby points at the junction of both the tube, let point 1 be in the air tube while point 2 be in the paint tube.

According to Bernoulli's principle, the air at point 1 is moving with some speed which causes the pressure drop inside tube 1, while at point 2 there is no velocity, so there is no pressure drop at that point. In fact, the pressure at point 2 approximately equals the atmospheric pressure.

As both the points are taken is nearby at the junction, to the pressure drop in the flow air pipe causes the suction of fluid from the relatively high-pressure tube (paint tube).

Hence, this rush of air creates low pressure, which sucks the paint up the tube and into the stream of air.