Keeping a cat safe in an appartment

Hi everyone.

I'm new here as a member, but I've been surfing this site for a while now for advice on my cats.

My question is this. My girlfriend and I have adopted 2 cats, Charm and Cupid. Cupid is 2.5 months old and Charm is 4 months old (and yes we will get them fixed when they are 6 months old :-) )

Charm was a stray that we adopted through the humane society. That being said, she's been outside before.

What concerns me is that I live 12 floors up and today I cought her climbing up the screen of my patio door. Now althought I have a balcony, I have other windows with no balcony, and should she climb that screen and go through it...well..I'd rather not think about that.

On the other hand I can't keep every window closed as it gets quite warm in here, especially with the building having cranked up the heat as we wait for winter to arrive (Winters are pretty cold in Ottawa).

Do you have any ideas on how I can secure my windows so as to allow a good air flow, while still protecting my cats from unknowingly injuring themselves?

I look forward to hearing from you all and I want to thank you for the great advice everyone has given out in other topics.

I use latticework to block my windows. You can buy one sheet of it at a local home store and cut it to fit, as it is plastic, it bends and wedges into the window frame, and the cracks between it (there are all sorts of designs) allows the air to flow. You can leave your windows wide open with no fear of a cat falling. Even if they push against it, and pop out the screen they can't get past the lattice work to fall. You can get them in the garden shop.

Welcome to the site!

I'm going to move this to Care and Grooming since it seems to be more of a care issue.

local shelters here will not let any animals leave without them being spayed/neutered (which is a good thing)

i'm suprised all shelters don't do this