For laboratory low-pressure gas lines (e.g., air, nitrogen for general purposes, pressure ≤0.5MPa), the gas tube selection should focus on flexibility, chemical resistance, and non-toxicity. The two most suitable options are:

• PTFE-lined stainless steel hoses: The inner layer is PTFE (resistant to most chemicals, non-toxic, and non-adsorptive), and the outer layer is 304 stainless steel braid (prevents hose expansion under pressure). They are ideal for gases that require moderate flexibility (e.g., connecting movable instruments).
• Polyurethane (PU) gas tubes: Lightweight, highly flexible, and easy to install. They are suitable for non-corrosive, non-toxic gases (e.g., compressed air for cleaning) but not for reactive or high-temperature gases (max temperature ≤80℃).

Avoid using PVC tubes—they may release plasticizers and are not resistant to organic solvents, which can contaminate gases or degrade the tube. Also, ensure the tube inner diameter matches the gas flow rate (e.g., 6mm ID for 0-50L/min flow).