The MUNI MP420 is a compact and lightweight 4-gas detector for worker safety at hazardous locations, with four standard sensors for oxygen (O2), combustibles (LEL), carbon monoxide (CO) and hydrogen sulfide (H2S). Alternative sensors are low-power infrared methane (CH4), sulfur dioxide (SO2), and hydrogen cyanide (HCN). The detector is packaged in a robust housing with no moving parts. Its battery power offers 24 hrs for a standard 4-gas detector, and extended runtime when using a low-power infrared sensor. The simple, 2-button operation results in ultimate ease of use and significantly reduced time spent training the user. To save user cost, sensors are not interchangeable and must be specified at time of purchase.