Which type of fittings should not be used in a low pressure CO2 system?

In a low-pressure CO2 system, the use of plastic fittings is not advisable due to their inability to withstand the temperature and pressure variations associated with carbon dioxide systems. CO2 can be stored in a liquid state at elevated pressures, and the fittings need to be capable of handling these conditions safely.

Plastic fittings may become brittle or deform under pressure or extreme temperature changes, which could lead to leaks or system failures. Malleable iron fittings, flanged joints, and stainless steel fittings are all designed to handle the rigorous demands of a low-pressure CO2 environment, ensuring reliability and safety.

Malleable iron fittings offer good strength and pressure resistance, while flanged joints allow for secure connections that can accommodate thermal expansion. Stainless steel fittings provide excellent corrosion resistance while also maintaining toughness and structural integrity under pressure. Thus, plastic fittings are the inappropriate choice for a low-pressure CO2 system.