Snowmobiling

While riding snowmobiles is fun, it can also be dangerous.
Head injuries are the leading cause of death and serious
injury on snowmobiles. Riders are nearly 2.5 times more likely
to die in a crash, if they are not wearing a helmet. So, always wear a helmet and ride responsibly.

Check the fit:

Before shopping for a helmet, measure your head. Determine the circumference of the widest part of your head using a cloth tape measure. Usually, this is 2.5 centimeters (one inch) above your eyes and ears, but take several measurements to ensure you have the largest area. You can also use your hat size as another starting point in determining your helmet size.
Using your head measurement or hat size, choose a helmet and try it on.
The helmet should fit snugly, but not so tight that it’s painful. It should have even pressure around the sides and top of your head.
The helmet should sit evenly on either side of your head with your eyes in the center. The top edge of the liner padding should sit just above your eyebrows.
To test the fit, grab the helmet with your hands on either side and try to rotate it from side-to-side and up and down. A properly fitted helmet will cause the skin to move as you try to move it. If your skin moves very little or not at all, or the helmet moves very easily, it is too big.
Make sure you cannot remove the helmet from your head when the chin strap is fastened.
Look in a mirror and examine the fit for gaps between the temples and the brow pad. Ensure the cheek pads touch your cheeks, without too much pressure.
A good way to confirm the helmet fits properly is to try on the same helmet in larger and smaller sizes and compare.

Additional tips:

Accepted standards are: Canadian Standards Association Standard D230, Snell Memorial Foundation, United States of America Federal Motor Vehicle Safety Standard, American National Standard Specifications for Protective Head-gear or British Standards Institute
Not every brand of helmet will fit every head size and shape the same, so don’t assume that if you’re a large in one brand, you’ll be a large in another.
Don’t be afraid to ask the salesperson or an experienced rider for assistance.
People often buy helmets that are too large. You may need to try a smaller helmet for a proper fit.
On many new helmets, the liner is designed to be a little snug at first, but will break-in after several hours of riding it to match the shape of your head.
Check the expiry date. An expired helmet may not protect you in a collision, as over time the padding and plastic wear down or crack, reducing its ability to withstand a crash.
If your helmet has taken a hard hit, discard it and buy a new one. The impact will decrease the helmet’s ability to protect your head in another crash.