Short answer: generally no
Brass PEX Ball Valves are designed for water systems. Gas lines have different requirements. Using water valves for gas is dangerous. Example: PEX tubing itself is not rated for gas.
Why PEX is not for gas
Gas can permeate through PEX plastic walls. This creates a safety hazard. Brass PEX Ball Valves are attached to PEX tubing. The combination fails gas code requirements. Example: natural gas can escape through the pipe wall.
Code restrictions apply
International Fuel Gas Code prohibits PEX for gas. Most local codes follow this rule. Brass PEX Ball Valves cannot be used legally for gas. Example: a home inspector will flag this immediately.
The valve body itself may be fine
The brass ball valve mechanism can handle gas. Many threaded brass valves are gas-rated. Brass PEX Ball Valves have the same internal parts. Example: if converted to threaded ends, the brass body works.
Connection type matters
PEX connections are not gas-tight for long term. Gas requires metal-to-metal seals or approved fittings. Brass PEX Ball Valves with crimp rings are not approved. Example: compression fittings with ferrules are also not gas-rated.
Example: propane line for a grill
A homeowner wants a shut-off for a gas grill. They see Brass PEX Ball Valves at the store. This would be a dangerous choice. Example: flexible gas connector hose is the correct product.
Example: natural gas water heater
A water heater needs a gas shut-off valve. The plumber uses a Brass PEX Ball Valves by mistake. The valve leaks gas through the PEX crimp. Example: a fire or explosion could result.
Approved gas valve materials
Gas valves must be listed for fuel gas service. Look for "UL" or "CSA" listings. Brass PEX Ball Valves typically lack these approvals. Example: a yellow-handled gas ball valve is a safe choice.
Pressure ratings are not the issue
Gas pressure is very low (0.25 to 2 psi). Water valves have plenty of pressure capacity. Brass PEX Ball Valves can handle gas pressure physically. Example: the issue is permeation, not pressure.
Why the confusion exists
Some brass valves work for both water and gas. These have special seals and approvals. Brass PEX Ball Valves rarely have dual certifications. Example: read the label carefully for "WOG" (water, oil, gas) rating.
How to identify a gas-rated valve
Look for "WOG" stamped on the body. Also look for "CSA 3.1" or "UL" listing. Brass PEX Ball Valves with threaded ends may have these. Example: a threaded brass ball valve from Apollo is often gas-rated.
Final verdict on gas use
Brass PEX Ball Valves should not be used for gas lines. The PEX connection method is unsafe. The tubing itself is not gas-rated. Only use valves specifically listed for fuel gas. Check local codes for approved products. When in doubt, ask a licensed plumber or gas fitter. Your family's safety depends on correct gas components. Example: spend a few extra dollars on proper gas valves for peace of mind.