Can You Use a Dirt Bike Helmet to Snowmobile?

I am all about having many different hobbies, but in some ways I have to save money and helmets are one of those things I feel I may be able to double use for multiple off-road hobbies.

My question was "Why is it that you can't use a dirt-bike helmet for snowmobiling? I would prefer to just buy one helmet to partake in multiple activities but that doesn't seem plausible." 

It sounds like from the comments that I can in fact use a dirt bike helmet for snowmobiling just using an insert or covering the vents so I don't freeze is the key.

There are ways that are even cheaper like duct tape to use to close the holes up on a dirt bike and help keep you warmer while riding. I think the biggest difference is the temperature. A snowmobile helmet is meant to keep you warmer and the dirt bike is meant to vent and help cool you off on warm days.

Thank you to Jason for dropping these two helmets on to give me an idea on what my size is and what would work.