Diagnosis
Yes, that's dangerous and needs immediate attention. A gas smell with knobs off indicates a leak in the fuel delivery system—likely at the tank connection, the regulator hose, or a faulty valve.
How to Fix It
First, turn the propane tank valve OFF. Do not attempt to use the grill. Mix a solution of dish soap and water. With the tank valve ON (but all grill knobs OFF), brush the soapy solution over all gas connections: where the hose connects to the tank, where the hose connects to the manifold, and around the base of each control valve. Look for bubbles forming, which pinpoint the leak.
If That Didn't Work
If you can't find an obvious leak at the connections, the issue could be internal, like a cracked manifold or a leaking valve seat. At this point, stop troubleshooting and contact Char-Broil customer service or a qualified gas appliance technician. Do not use the grill.
Heads Up
Never, ever use a flame to check for a gas leak. The soapy water test is the safe, standard method. If you ever hear a hissing sound or smell gas strongly, turn off the tank valve, move away, and don't operate any electrical switches nearby.