If you're finding that your air isn't as clean as you want it to be or you have noticed an increase in allergic reactions, you might be thinking about buying a new air purifier. If this is the case, consider checking the filter first and make sure it doesn't need to be replaced. In most air purifiers, the filter does all the work, so if it's not working at its usual capacity, the filter is probably to blame. However, if the mechanical hardware — like the fan, control panel, or air quality sensors — breaks down, you'll want to get a new purifier.