Charcoal canister purge valve question

[howzzzit]

How might I check the purge valve on my 72 C10 charcoal canister to verify if it's good or bad? Another question is why is it needed if one of the lines is connected to the pcv line? Seems like it would constantly be purging the gas fumes. I also think I read the purge valve should be connected to ported vacuum? Right now the only thing connected to the canister is the 3/8 fuel line. I don't smell gas fumes, but would like to hook it up correctly. Thanks.