Mystery vent on 737-300

[CaptainSandL]

I have recently noticed this small vent on a couple of old 737-300’s and nobody seems to know what it is.

http://www.b737.org.uk/stbd_vent.jpg

The vent is a hole approx 1 inch in diameter with a cover that is open toward the rear. It is only the stbd side of the fuselage about 2m forward of the leading edge. The aircraft was built in March 94 (L/N 2594) and was originally delivered to Maersk Air.

Any ideas please?

S & L

[Mr @ Spotty M]

I think it might be a aux fuel tank vent.

[CaptainSandL]

I think you could be right, the aircraft did have an aux fuel tank.

Mystery solved, thanks.