Question:
Can the LEL sensors in the GfG instruments detect gasoline and kerosene? And can they measure the vapors of these petroleum derivatives?
Answer:
Catalytic LEL sensors can be used for gasoline, but are not recommended for kerosene. The problem is the size of the molecules in the kerosene. The larger the molecule, the slower the sensor responds, and also, the lower the relative response. Another problem is that the toxic exposure limit for heavy fuels like diesel, jet fuel and kerosene is very low. The TLV for gasoline is 300 ppm. The TLV for kerosene is only 30 ppm.
The 100% LEL concentration for kerosene is 0.7% volume (= 7000 ppm). That means 10% LEL kerosene = 700 ppm. If you use a catalytic LEL sensor, and set the alarm at 10% LEL, even if the sensor responded perfectly for kerosene, it would take a concentration over 23 times higher than the exposure limit to activate the alarm.
For this reason, we usually use a PID sensor to measure kerosene and gasoline vapor, which allows us to set the alarm at the ppm toxic exposure limit. You still have an LEL sensor installed in the instrument, but you take action at the toxic exposure limit concentration.
Also, if you decide to use a catalytic sensor to measure gasoline you should use the non-filtered version of the CC LEL sensor. The standard CC LEL sensor is warranted for 3 years , but the unfiltered LEL sensor is warranted for 2 years.
Another approach is to use an infrared (IR) LEL sensor to measure explosive range concentration gasoline and kerosene. The IR LEL sensor responds better than the CC LEL sensor to these vapors. However, you still have the issue of taking action at the TLV rather than taking action at 10% LEL. Also, since IR LEL sensors cannot detect hydrogen, we normally include an electrochemical hydrogen sensor in any instrument that includes an IR LEL sensor.