After two weeks down time, signal has doubled

[unhpian]

I have somewhat of a mystery on my hands. We have a PE autosystem w/ FID and a RTX 5sil column which we are using to screen for PAHs. About two weeks ago, I shut the GC off, and turned off the hydrogen and air, but left the carrier gas (nitrogen) on. When I turned it back on today and ran some standards, the signal has almost doubled. We are running the same exact method, gas flow rates are identical (I checked with a meter), and I even tried running some old standards to rule out mixing error, and those are double too. No one else would have touched but me - so why has signal suddenly doubled after being off for a few days? Not that I'm complaining - I've always thought it should be higher - but I want to keep it that way and find out why it's happening.

[aldehyde]

Are you talking about baseline signal or the area counts/response of your analytes?

[Peter Apps]

Is it exactly double, or just more or less double ?

How are you doing the injections - autosampler or manual, and what syringe (type and volume) are you using ?

Peter