Rim size is 622×19, what's the narrowest tyre I can run on them?

I have a Scott sportster hybrid bike which I’m going to use for commuting, it came with conti tour ride tyres which have to much tread for my liking,
It has a sticker on the rim saying ETRTO 622×19
Current tyres are 700x37c,
What is the narrowest I can go?

Cheers

You should be able to get a 28mm tyre on there – and all evidence now suggests there is no benefit from going any narrower.

Something like this perhaps?
http://www.tweekscycles.com/components/road-clincher-tyres/continental-grand-prix-4000-s-ii-tyre

though for commuting I’d prefer something with a bit more puncture prevention..
http://www.tweekscycles.com/components/road-clincher-tyres/continental-grand-prix-4-season-vectran-duraskin-tyre

I liked my gp4 seasons. I’m using 25mms on Crest 29er rims. They lasted well but finally died so I’m going up to 28mms.

http://www.schwalbe.co.uk/_webedit/uploaded-files/All%20Files/Technical%20Info.pdf
Page 7 is your friend

I use 25mm Michelin road tyres on a 19mm rims. They measure 27,2mm across at 100psi.
Excellent. I am sure that various experts came up with 25mm as being the current optimum. Bigger does continue the idea that the contact patch is better but weight increases counteract that. Possibly 28mm tyre will get narrower