IR29 D Transmitters - Monitoring combustible gases. If you need to monitor combustible gases and vapors in Ex zones, the IR29 D transmitter is a reliable and robust solution. It uses an analog (4-20 mA) signal to transmit measured values and status information. Measured values are shown on its LC display. Gases are monitored either on site by diffusion or by pressureless gas supply using a flow adapter. In combination with one of GfG's reliable controllers, the IR29 D can be installed in new gas detection systems or retrofitted into existing ones.