PDM+ is a single sustainable gas monitor designed to detect oxygen deficiency or the presence of toxic gas in the ambient environment. The PDM+ is sustaniable, hence its battery and sensor can be replaced. When turned on, PDM+ continuously monitors ambient air for the presence of a specific gas and alerts the user to potentially unsafe exposure with LED, vibrating, and audible alarms. After use, the instrument can be turned off, making the battery last up to three years. The PDM+ is easy to wear, the backside of the device has a strong metal clip to secure the monitor to a shirt, belt or helmet.