Which is better to put in my room for improved air quality: an air filter or purifier, or a plant?

Plants might make the room look pretty.

Some people are allergic to house plants or to the dust or mold they or the soil might harbor.

But a quicker fix is to just have an air purifyer.

Be sure to vacuum and dust your room, house and heating vents on a regular basis.

If you have dry winters and humid summers you might also consider a humidifier and dehumidifier.

I love lots of plants in the house, but I would say for improving air quality a purifier would have a larger capacity and output... mostly because it's actively purifying the air and pushing clean air out, while plants are doing it in a more passive manner. Plus, purifiers will take out your particulates (the dust, pollen, dander, etc.), which plants will NOT remove. So, get a purifier AND a plant! One of the best plants would be a boston fern - it removes lots of toxins from the air, such as formaldehyde, benzene and toluene, which are actually found in many homes. Formaldehyde, I just read last week, is found in many new clothes from the manufacturing process, as well as adhesive breakdown from particle board in homes! Also, plastics, paints, etc. give off these aromatic hydrocarbons & aldehydes. Some purifiers may remove these, I think most do, you'll have to check the specs. But live plants also add lots of cheer and personality to a room, so I'd go with both :)

While the plant is the active partner producing oxygen and using CO2 it is the soil microbes that do the greater part of air scrubbing. Plant Studies showed air cleansing took place between the soil and air surface. The actual work is done by "common soil microorganisms" most of which are "known to be capable of biodegrading toxic chemicals when activated by plant root growth." Practically this means a broader pot with exposed soil to create an air soil exchange surface. Do not allow the plants to cover the entire soil surface.

http://www.practicalasthma.net/pages/topics/aaplan...

As few as 15 houseplants, in an average 2,300sq ft home, can significantly reduce the quantity of indoor contaminants.

http://www.plantea.com/houseplants.htm

http://www.thegreenguide.com/blog/tow/kw/indoor_ai...

A west facing window can become very hot in the summer so you need to watch that the plant does not become heat & water stressed. It is possible for a plant to become hot enough that it will transpire (lose water) faster than it can take water up by its roots and wilt. http://herselfshouseplants.com/2007/08/plants-for-...

http://www.coopext.colostate.edu/4dmg/Plants/windo...

My mother once told me not to have too many plants in my bedroom because at night they do not photosynthesis but they continue to respire and if you are not in a well ventilated room you would be competing with the plant for oxygen...I'm imagining that it would take rather a lot of plants for there to be any risk of this happening - plus I'm sure all the oxygen they churn out in the daytime more than (or equal to) compensates for the oxygen they suck in at night. Also think of the therapeutic benefits of having a plant in your room. they are beautiful and they will not make a horrible buzzing noise as I imagine the electronic "environisers, filters" make...

I hope that helps, if only a little bit, best wishes xx