If you just want to use it in the ward, to avoid respiratory diseases, I recommend BLUEAIR, after all, people in the United States is to the status of the second level of medical equipment to use, the price is relatively cheap, and quite practical, does not take up space.
It depends on your personal needs. You can take a look at their website if you have further needs, and you'll get an idea.
If you are still not too clear, you can continue to ask me, I specific questions, specific answers.