Question: how many ppm is 1 lel?
Answer: The lower explosive limit (100% LEL) concentration for hydrogen is about 4.0% volume, which is equal to 40,000 ppm. So, 1.0% LEL hydrogen = 40,000 ppm X 0.01 = 400 ppm. So, a concentration of 2000 ppm hydrogen = 2000 ÷ 400 = 5.0% LEL.