Imagine being....
in a car with no A/C
in a windowless room
in a sauna
or other places with no ventilation where it's hard to breathe.
This is what it would be like for your hamster if their enclosure didn't have ventilation.
Except your hamster can't simply move to another room if it gets too stuffy.
Adding more slots in an enclosure allows for more air flow to move through the enclosure.

Not only can your hamster breath clearer, but this also prevents condensation from building up and potentially molding things.
*This can still happen, but the risk is minimized when ventilation is increased.
Happy Hamstery Home
Over 4x the ventilation of enclosures like the Niteangel Vista! The lid features 20 large ventilation slits- more that double the previous 8. The final model also includes high ventilation slits along the back, front, and sides for significantly improved
airflow while keeping them out of reach to discourage climbing and chewing.