MSA Altair 4XR Multigas Detector LEL/O2/CO/H2SMSA Altair 4XR Multigas Detector LEL O2 CO H2S ALT4XR Charcoal case with LEL 0 100% Pentane, O2 19. 5& 23%, CO 20 100 100 20 ppm, H2S 5 10 10 5ppm. Outfitted with rapid response MSA XCell sensors, the ALTAIR 4XR Gas Detector is the toughest 4 gas monitor on the market and is backed by a 4 year warranty. The ALTAIR 4XR can also provide real time incident awareness to team members, supervisors, safety managers and others when paired with the MSA ALTAIR