c6d25c5f_r_s_Frequently_Asked_Questions__Definition
[Term] HPA or Compressed Air [Definition] 
High pressure compressed air (3000 to 4500 psi) is usually used instead of CO2 in tournament paintball. The use of HPA requires specialized high pressure tanks and regulators which lower the output pressure to what the paintguns can handle.
WARPIG's Beginner's Frequently Asked Questions
Definition