Common gas hazards include: Carbon Monoxide (CO), Combustible Gases, Hydrogen Sulphide (H2S), Nitrogen Dioxide (NO2), Nitric Oxide (NO), O2 (Enrichment/Deficient), Sulphur Dioxide (SO2) and Volatile Organic Compounds (VOC).

Personal gas detectors form an integral part of onsite Personal Protective Equipment (PPE) in construction of trenches. When earth is dug up, there is a danger of disturbing gases such as Methane or Hydrogen Sulphide that arise from the ground.