How do you expect a fan to run without electrical power and a way to turn it on (and off when not needed)? I suppose battery-operated is a possibility but it'd be less powerful and bring in the inconvenience of dealing with battery replacement or recharging.

I suspect the vent is part of the HVAC. Sarah Sarah, can you post a picture of the vent, not a close up, but maybe 5’ away.

Yes, I was wondering if there was something battery operated and had a switch on the fan or even a pull chain. Anything that wouldn’t require an electrician.

*switch directly on the fan

Battery operated exhaust fan. I reccommend looking at those.

I do not think anyone on this site has any experience with one.

Where are you located?

Thanks A Mat. I have been looking/googling and can’t seem to find any. We are in NY

Does it actually vent to the outside now? Or is it just a grate that attaches to your furnace or air conditioning and the outside wall is behind it? If it vents to the outside and you can open the vents, just get a battery operated wall fan and hang it from the grate to suck some air to the outside. It won't be that efficient but maybe could work. But I don't know how you keep the weather out if it's actually open to the outdoors.

Even if you say no electrician is that because of money or that you cannot open walls? if the later, you might be able to have it wired using conduit instead of inside the wall - I don't know if code allows that, esp in a bathroom.

"Is there a way to add a fan without having to wire it and without having to attach it to a switch?"

Sure. Lots of ways. I won't mention the battery-powered version since that's already been noted by others as an option.

1. You could install vent duct from the exterior to a level above the roof and cap it with a wind turbine ventilator. Totally mechanical. It will work better on windy days, but you can't have everything.

2. You could install a fan with an air-powered motor and run plastic tubing from an air compressor located in your garage. A side benefit is that this arrangement would be suitable for explosive environments.

3. You could install a small water turbine in the water line to the shower. It would generate 12 volt DC which can power a 12 volt fan. It would run only when you're using the shower, but then again, that's when you need it most. I know this option involves wiring, but it's all low-voltage wiring so you could do it yourself without risk of electrocution. Well, at least if you don't try to install it while showering. Multi-tasking is great, but it comes with some risks.

4. You could install a nozzle inside the duct and use water as the motive force. This is the same principle that firefighters use for ventilating buildings using fire hoses. You may be able to direct the exhaust stream to your garden so you'd get points for a "green" option.

5. You could install a solar-powered vent fan. Your shower options might be limited to sunny days, but there's probably an app for your phone that would coordinate shower schedules with the weather forecast. Plus, you can order them on Amazon and get one in a day.

Thank you all. I should have mentioned this is in an apt. I have looked on google endlessly and can’t seem to find a battery powered exhaust fan to put into the existing vent cutout.

Clip fan looks like it might be a good idea

" I should have mentioned this is in an apt." Oh, well, some of my best ideas go in the trash can. Although not everyone considers them in the "best" category.

If that vent is not vented to the outside, and has to do with airflow to the ac, or even put out heat, then you cannot use a fan to put moist air into it.

No central air. Heat comes from a unit under the window as well.

Well, you still need to see if it vents to outside, since, its a receipe for mold, etc if you put moist air into the vent.

Instead of revealing pertinent info piecemeal, post a photo please. Of the window, the vent, the 'unit' under the window...