Air Filter/purifier recommendations?

Turns out my daughter probably has asthma....She is in middle of diagnosis. I read a suggestion on a website that recommended the Whirlpool Whisperpure. It gets pretty good reviews on Amazon. I looked it up on Consumer Reports who doesn't seem to cover that brand. Just wondering if anyone here has had any experience with this?

I don't (have experience with the WW).

As you are considering this, presumably you home does not have a forced air furnace (which could be fitted with a "whole house" media filter).

We have a steam boiler and I would like to see input on this question as well. Thanks in advance.