You are allowed to travel with your inflatable PFD with the existing CO2 cartridge installed in the PFD, plus two (2) extra replacement cartridges. You can only pack/take one inflatable PFD, per person and per checked bag. To help minimize the chances of your inflatable PFD being removed from your bag, you should print copies of the web pages which show they are legal to pack in checked luggage and tape a copy to the PFD, so if there is a bag search, the inspectors will see the paperwork and, hopefully, determine it is safe to leave them in your bag.
Here is a link to the Canadian Air Transport Security Authority which answers questions about what you can and can't bring on a plane.
Here's a link to the Transport Canada website that shows what you can and can't carry. Print a copy and put with your inflatable PFD in your checked luggage.
If our customers are coming back from the US, then this is the link to the TSA (Transportation Security Administration) site that shows you can have up to 2 CO2 cartridges in the PFD and two (2) extras.