http://www.natlallergy.com/prod/1580/honeywell-enviracaire-50250-hepa-air-cleaners.html

How do I know? Recommendations?

My two Honeywell Enviracaires (different models) have lasted for a very long time. One is at least 15 years old, the other is seven or so. They run great, but you'll have to get used to the white noise (constant airflow). There are quieter units, but I live in a city and like having the extra white noise buffer.