Terraces and the dangers of living high
If you are lucky enough to have a balcony or terrace in your apartment then this will need to be made cat proof prior to introducing your cat. Cats are athletic and can balance probably better than most gymnasts.
However, the Maine Coon has an Achilles heal when it comes to flat slippery surfaces and modern living design. Your Maine Coon has tufts under their paws. This creates an ice rink skating effect that they are never quite able to control. Especially if your cat becomes skittish or surprised they are likely to leap without thinking. You cannot predict how your cat will behave in an un unprecedented situation. So if you value the life of your Maine Coon you need to secure the terrace.
You can secure a balcony with either fine metal netting (although this requires a professional fitter to deliver a respectable and practical finish) which can be expensive but will endure.
A temporary solution and a quick solution is to use a fine plastic netting. I have included images on this page showing this solution. This is a cheap and immediate solution. The netting does deteriorate overtime and will need to be replaced every couple of years.
Opening windows and unassuming dangers
Your Maine Coon is large, heavy, long and lithe. Your cat will explore every angle of your home and try anything in that space. Generally they prefer difficult to reach spaces. They are the masters of fitting large mass into small areas. This will cause you many anxious moment as you will no doubt think you have lost your cat, when instead he is hiding on the top of your wardrobe or in a kitchen cupboard.
Here is the danger. Most modern windows allow for the window to be opened angled from the top. Your Maine Coon will try to explore the window opening and will get lodged. The more your cat struggles the deaper he will become logded, breaking bones in his ribcage and slowly causing him to suffocate.
So what is the solution. If you are clever you may make some netting to close the opening of the window. Although storage can be cumbersome and time consuming to put into place.
Ideally you need to either close the window or fully open then window. If the window is fully open you will need to have fly netting securely in place. Indeed, the fly netting will also be tested by your Maine Coon, so make sure you have the click shut variety installed.
If you find that you can’t fit netting then the only real solution is to keep your windows shut. I would suggest investing in an air conditioning unit as a good solution. This will keep fresh air circulating in your house without the need to open windows.