Specifications: Main chip: the LM393, MQ-8 gas sensor Working voltage: DC5V With a signal output instructions. Dual signal output (TTL level output and analog output) TTL output valid signal for low level. (when the low output electric signal lights at ordinary times, can be directly pick up SCM) Analog 0 ~ 5 v voltage, the higher the concentration, the higher the voltage. High sensitivity to hydrogen Can be resistant to ethanol steam, LPG (petroleum), smoke interference Has a long service life and reliable stability Quick response recovery features Size: 35 x 20 x 21mm/ 1.4" x 0.79" x 0.83" (L*W*H)