Can I top off foreline pump oil without venting?

[rosemaryandsage47]

My Duo 2.5 foreline pump does not have a mist filter so it loses oil throughout the months. I typically fill it halfway, but it's crept down near the bottom oil mark. A poweruser in the Agilent forums suggests to fill it to near the top mark and I can add oil without venting the instrument. He says there really isn't a safety risk but I'm unsure. Anybody done this?

[trozen]

you can refill dual stage pumps while running

I've never done this on Duo 2.5, but since it is a dual stage, you should be okay, just do not open it for too long

[James_Ball]

I have never had trouble adding oil to a running pump. It can be a little noisy and you get some mist from the opening while filling but that is about the only problems.