Crowcon Tetra 3 [T3R-04-NC-Z] 2-Gas Personal Monitor without Multi-regional Charger, CH4 % LEL, O2 (2yr). The Tetra3 multigas monitor is a compact, robust and easy-to-use diffusion based detector. Single button operation, small size and clear top-mounted display make it a favourite in the market amongst those working in demanding industrial environments, such as those in the water, telecoms, food, brewing or hydrocarbons sectors. Reliable: Based on tried and tested Tetra instrument; Proven sensor technology and software operation; Simple indications of operating status can be viewed at a glance; 30 day countdown warning of calibration due date. Performance: Li-ion rechargeable battery gives >16 hours operation; True single button operation - the most user friendly range available; Easy to read backlit graphic display for gas readings and diagnostics. Robust: Tough plastic construction to resist even the toughest shock and vibration; Over-moulded rubber for added protection; Water and dust resistant to IP65 and IP67. Alarms: 95dBA audible alarm; Piercingly bright dual red/blue visual alarm; Internal vibrating alarm; Two levels of instantaneous alarm; Time weighted average alarm for 8 hours and 15 minute averages.