Building snow forts is a classic winter-time activity, something done by children the world around. But the wrong type of snow fort can be dangerous enough to kill them.

Though it may not look it, snow is heavy, especially if it’s been compacted in any way. If a child is building a snow fort through compacted snow and it collapses or caves in on them, they can wind up just like an avalanche victim: Buried under a pile of snow with no way to breathe. The weight of the snow might be heavy enough to prevent their chest from rising to inhale, and any air they might have access to under the snow will quickly run out.

What commonly happens is that children build tunnels through the large piles of snow left by snow plows. If a child is digging a tunnel through the bottom of one of these piles and it caves in on them, they’re in serious trouble. Young kids don’t have the muscle strength to pull themselves out, especially if it collapsed while they were in a prone position. Unless an adult can get them out quickly, they’ll soon suffocate.

Safely building snow forts with your children

To ensure this doesn’t happen to your children, take the following safety precautions:

1. Adult monitoring is always advised anytime kids are out playing in the snow. If you want to build an elaborate snow fort, do it alongside them to ensure it’s done safely and you can pull them out if anything happens.

2. Talk to kids about this danger and explain why they shouldn’t build tunnels through the bottom of snow piles. To demonstrate how heavy snow can be, take a big shovel, scoop up a big pile of compacted snow, and then have kids try to lift the shovel from the end of the handle. Most will struggle. Now tell them to imagine lifting dozens or even hundreds of these shovels at once. This is what it would be like if they were digging a tunnel through the bottom of a large snow pile and it collapsed while they were inside it.