This kit provides everything you need to calibrate the Carbon Monoxide monitor on an Allegro Industries worker filtration panel (also known as a breather box). For use on Allegro's Carry Air, Wall-Air and Oil-less Compressors, this kit includes a gas cylinder each of span gas and zero gas, as well as a constant-flow regulator and tubing. The kit comes in a plastic carrying box so all your calibration tools are together when you need them. Note: calibration gas is not returnable. Please check your selection carefully before ordering.