what is the name of the ceiling fans useally in bars that look like a wagon wheel and supposed to trap smoke?

The name of the product is called the Purifan. Before you run to their site to ask the shoe salesman if you need shoes, take a look at http://www.smoke-eaters-supply.com/ceiling-fan-smo... Not only is it physically impossible for the Purifan to work, but they won't even pay for testing to show whether it works or not. We have several customers who have tried the Purifan and then call us to get a machine that really works. We don't gain customers from bad-mouthing the competition, we get customers because the machines we offer do the job. The information (about the Purifan) on our website comes directly from their site and makes the argument that they can't even tell the truth about their own products. If you have more questions, feel free to call or email. I hope this helps.

An exhaust fan.