Checking to see how much filter replacements cost is important. If a unit has two filters, for example it has a HEPA filter as well as a carbon filter, the filters may need to be replaced at different times. An air purifier is only effective if the filters are cleaned and maintained. Replacing the filters regularly are important to getting the most out of an air filter. Some manufacturers of air filters actually require the user to regularly replace the filter to keep their warranty valid. Even best air purifier for pets dander will need a filter replace.
Some air purifiers are virtually silent, while others are quite noisy, especially when operating at their highest power. Some purifiers with a slower fan can have better results because of their thick filters. However, a slow moving fan might not push enough air around the room to thoroughly clean it. Balancing the noise level vs. the productivity level of any filter can be difficult.
Generally, each air filter has a happy medium between its efficacy and its noise level. When buying an air purifier, one can ask for a demonstration to determine if the noise level of that particular filter is appropriate for the home.
A warranty is a safe thing to have while buying an air filter, and they are typically standard. It is important to know what the warranty covers. The motor, the fan, and the electrical components are all things that should be covered under warranty. It is also good to know what user actions will cause the warranty to be void. As previously mentioned, some manufacturers will not honor a warranty if the filters have not been replaced as recommended.