The thing people don’t tell you about a lot of statistics is that there is always a variance. When you those numbers in the news articles or even on your medicine bottle, you need to remember that this might not always be right for you. For example, I take a 2000 milligram vitamin D pill each and every day. I do this because I live in the north and sunlight is scarce much of the winter. My brother on the other takes a 50,000 milligram vitamin D pill once a week, because his chronic illness requires it of him. Though my bottle says ‘do not exceed dose unless directed by a doctor,’ he has exactly that. Well, the same can be said of your car and your HVAC system. If you put your car through the paces, you’ll need to change the oil more often. If you have a lot of pets or keep a fairly dirty home, you’ll need to change your air filter more. Most HVAC supplier websites will tell you that you need to change your air filter at least once a month on average–on average being the fine print here. The average does not apply to everyone! I change my air filter once a month because I have one cat, vacuum and dust often. My mother in law has four dogs and a small house. She lives with plenty of yard space for the dogs to run around in. However, that small house plus four dogs means a lot of pet hair. So my mother in law changes her air filter at least every two weeks. Be sure to take stock of your household and find the best air filter schedule that’s right for you.