Question 724 Deck Safety

The correct answer is D) Over the flammable range. The rapid movement of the needle on the combustible gas indicator to 100 on the dial, followed by a drop to zero, indicates that the gas concentration in the tank sample was above the flammable range. When the concentration of flammable gas in the air is above the upper explosive limit (UEL), the gas mixture is considered "over the flammable range" and cannot ignite or explode. The other options are incorrect because: A) The rapid movement of the needle suggests the instrument is functioning properly, not giving a false reading. B) The concentration being above the UEL means it is not within the flammable range. C) The concentration being above the UEL means it is not less than the flammable range.