PVC pipes can be used for air applications, but you should stick to passive systems, especially systems that only need PVC outlets. This means using PVC pipes for exhaust vents in plumbing systems, or for basic air lines needs for venting. Connecting PVC pipes to metal pipes can be problematic, since the two contract and expand at different rates and may lead to cracking over time.
One of the most common air-based uses for PVC pipe is in compression systems, where the air needs to be blown out with force, often for detail and sanding work. While this may seem like a logical use of lightweight PVC pipe, PVC is not designed for compressed air systems. It is a brittle plastic material, and under compression it has the potential to shatter or crack, which can lead to both danger and damage.
PVC is not an ideal air line material in other cases, too. If you are planning on using PVC in an application where you will need to take the pipes apart and replace them frequently, this can wear down the ends of the PVC pipe and lead to bad connections with leaking air (another reason compression systems should not use PVC). Air systems that create frequent vibration can cause similar issues with PVC, even when it is bonded.
The alternatives to PVC piping include many benefits. HDPE (high-density polyethylene) piping, for example, is another plastic option, but has more inherent flexibility than PVC and will not crack or shatter as easily. There are other newer thermoplastics with similar advantages. These will cost more than PVC but may be better suited to air-based applications, especially when dealing with compressed gases.