I have a gas fired hot water boiler. I have noticed there is gurgling or air in the system. Where in the system would I go to purge the air out?

There is no one-size-fits-all answer to that. Most commonly, the individual radiant terminals have a key vent that is opened to allow air to escape. Are your terminals free-standing, wall-recessed, or baseboard convector type?

They are baseboard type

Have you checked the water pressure at the boiler, maybe you have all air and no water. How many zones do you have? If it was setup right you can flush each zone seperatly for the boiler.

I have seen 2 methods for venting air from these: 1) key vents inside the enclosure, 2) purge valves in series with shut-off valves. You should have one or the other.