We had a first aid instructor come to playgroup last week, and she is also certified in car seat safety, I just thought I'd pass on a few of the things she taught us about car seats, b/c I had no idea about some of them, and it was putting Kallie at risk!
She told us that there should be NO bunting bags in the carseat whatsoever (the kind that goes underneath and over...the kind that just goes on top is ok), and that babies/toddlers/children should NEVER wear snow suits or puffy winter jackets in their carseats. The reason is that in an accident, any extra material can compress and the baby can slip right out of the straps. This has happened many times, and is almost always fatal for the child. I had no idea about that, Kallie was wearing her snowsuit in her carseat all winter. The woman said that we probably wouldn't like the info she gave us, b/c it's impractical (hello, no snowsuit in -40 weather?!?!?), sometimes not economical (buying a 'transition' carseat to make sure your child is in the proper weight range for their seat) and can just be more work. But it's the safety of your child that's most important.
A couple of other things she told us: You can't buy a carseat in the states, it has to have the Canadian 'seal' to show it's been regulated by Canadian government (even though it's probably the exact same one as you'd buy in the states, and was probably made there). If you're pulled over and they notice it's not Canadian regulated, you can get a huge fine. And babies should be rear-facing until a minimum of one-year AND 20 lbs. If they turn one and they're still not 20 lbs (which will be Kallie) they have to stay rear-facing until they reach that weight. If they weigh 20 lbs before 1, they have to stay rear-facing until 12 months. And carseats have expiration dates on them (I did not know that), usually stamped right into the plastic. They last for 6-8 years usually. And if you're ever in an accident, you should buy a new seat, b/c you have no idea what may have happened to it in the impact, even if it doesn't seem to have been affected (that would be the non-economical part).
Anyways, I may have just been in the dark and everyone already knows all this, I knew some but a lot surprised me and the mom's at playgroup. Hope this is helpful to someone!