On 2005-12-01, Mike wrote:

We have natural gas. I just took a look. The vent is actually on top
of the meter and connected to a circular piece of metal.

That circular piece of metal is the regulator. It drops the natural
gas pressure down from the higher distribuation pressure in the street
(several psi?) to the lower pressure in your house (typically 0.25
psi). All regulators have a vent like you describe, but I don't know
whether it is normal or not for natural gas to be discharged from it.

Cheers, Wayne