When buying an Air Purifier, what should I look for?

I am wanting to purchase an air purifier for my apartment, which is approximately 700 square feet. I am wanting to eliminate light cigarette odor, pollen, dust, and perhaps pet dander in the future.



What should I look for when purchasing a purifier? Are their particular brands, features, styles, designs, etc, that I should look for?



Any product recommendations? I am looking for a price range of $75-$150 (USD)



Thanks for the advice!

When buying an Air Purifier, what should I look for?
i have had a Oreck tabletop purifier for 6 years but i paid around $350 for it .... I never have to buy filters so i save lots of money there ......i love it...i rarely have to dust and when i do it's a light film...not like before i got the filter, after a few days the dust use to be thick everywhere......i no longer have a musty/ moist smell during the summer when it gets really humid here..hope this helps :o)