The internal treatment of the cylinder varies by gas type. Industrial gases (Oxygen, Nitrogen, Argon) use standard steel, while corrosive gases or high-purity specialty gases require internal polishing or specific linings, increasing the price. For LPG or Propane, lightweight welded steel is common, whereas Medical Oxygen cylinders must adhere to stricter hygiene and material purity standards. Ensure the color coding matches the international standard for the specific gas to avoid operational hazards.