As you explore the first area of Stray, Dead City, you will run into your first challenge, getting past a ventilation fan. Okay, this is technically the second challenge after a pool of toxic-looking goo, but that was just a simple jumping tutorial. Dealing with the fan is actually very simple, you just need to look around.
How to stop the fan in Dead City
Stopping the fan is simple, you just need to find something to drop in front of it. Turn around and hop back down the pipes you used to climb up to the fan. At the bottom, toward the left, you will find a small can that you can interact with. This will be on its own, ignore the three that are grouped close together.
Interact with it to pick it up, then climb back to the top of the pipes. Move toward the fan and when you are at the top of the slop, drop the can. It will roll down toward the fan and become wedged between the spin arms and one of the supports. This will allow you to get safely through the gap.
This puzzle is really just a small introduction to what will become the basis of your time in Stray. You will need to explore and pay attention to the environment that you are in to move the story forward, and figure out how to affect it despite being a cat.
How to stop the second fan in Dead City
After some more exploring, players will come across a second fan. This one can be deactivated by grabbing the power cell out of the wall on the left. Interact with it to grab it and this will cause the fan to power down, allowing you to jump up through the gap.