Grove - Gas Sensor(MQ-2)：Combustible Gas Smoke [medium sensitivity]
Grove - Gas Sensor(MQ-3)：Alcohol and Benzine [high sensitivity] Long warm-up
Grove - Gas Sensor(MQ-5)：LPG, Natural Gas, Town Gas [high sensitivity]
Grove - Gas Sensor(MQ-9)：LPG, CO, CH4 [low sensitivity]

Note - Gas sensors need to be heated, first minute the data is incorrect.
