1. LEL (Lower Explosive Limit):Definition: The lowest concentration of a gas or vapor in the air that can ignite and produce a flame.Where Found: Commonly associated with flammable gases such as methane, propane, and hydrogen.Effects on Body: LEL itself doesn't directly affect the body at lower concentration (less than 5 %), but if ignited, it can cause fires or explosions with potential harm.Levels:Above zero : NO hot workUp to 5 % : Cold work only5% To 10% : SCBA Needed2. H2S (Hydrogen Sulfide):- Definition: A colorless, flammable and toxic gas which is than air- Where Found: Produced in industrial activities such as oil refining and wastewater treatment etc- Effects on Body: Inhalation can cause respiratory irritation, headache, dizziness, and in severe cases, respiratory failure and death.LevelsPEL 10 ppmIDLH 100 ppm3. CO (Carbon Monoxide):- Definition:A colorless, odorless gas produced by incomplete combustion of carbon-containing fuels.Where Found: Commonly emitted by vehicles or other fuel-burning appliances.Effects on Body: Binds to hemoglobin in the blood, reducing its ability to carry oxygen, leading to symptoms like headache, dizziness, and potentially fatal carbon monoxide poisoning.LevelsPEL : 35 ppmIDLH :1000 ppm4. Oxygen:Definition:A colorless, odorless gas essential for life, used by cells to produce energy through respiration.Where Found:Present in the Earth's atmosphere about 21% of the air we breathe.Effects on Body: Necessary for cellular respiration and vital organ function; oxygen deprivation (hypoxia) can lead to shortness of breath to loss of consciousness and death.Levels20 % TO 23.5Gas test frequencyEvery 2 hour or as per CSE PlanGas detectorsMx4Mx6T40