When sourcing CO2 nozzles, you must prioritize material durability and thermal resistance. CO2 is discharged at extremely low temperatures (approx. -78°C), so the nozzle must be made of high-density polyethylene (HDPE) or specialized frost-resistant plastics to prevent cracking or 'cold burns' to the user. Ensure the thread specification (e.g., W21.8, M10, or 1/2") matches your existing valve inventory to avoid leakage. Additionally, verify the discharge horn geometry, as it directly affects the gas expansion rate and fire-smothering efficiency.