As a general rule, HVAC air filters should be replaced every one to three months (or every 90 days). However, the ideal frequency depends on several factors, including the filter type and your home's environment. For instance, if you use thinner filters (1-2 inches deep), have pets, have household members with allergies, smoke indoors, or frequently keep windows open, you may need to change the filter as often as once a month. It's best to follow the manufacturer's recommendation as a guideline and visually inspect the filter monthly to see if it's dirty. Regular filter changes are crucial for maintaining proper airflow, good indoor air quality, and efficient HVAC system operation.

The effectiveness of an air purifier is heavily dependent on its size. While portable air purifiers are best for single rooms or limited areas of the house, whole-house air purification systems are installed within the HVAC system to provide filtering for the entire indoor space. Discussing your needs with your installation company is the best way to determine what type and size of system your home requires. 

If you don't regularly change your HVAC air filter, it will become clogged with dust, dirt, and other contaminants. This blockage forces the system to work harder to circulate air, leading to several negative consequences. You may experience higher energy bills, poor temperature regulation, reduced air quality, and slower system performance. Over time, this added strain can cause parts to break more frequently, lead to system failure, and ultimately shorten the lifespan of your entire HVAC unit. In some cases, it can also contribute to health problems. It's recommended to change the filter at least every three months.

Always turn off the power to your HVAC system before you remove the front cover to replace the air filter. If there isn’t an off switch, turn it off at the circuit breaker box. This prevents the risk of electric shock and stops unfiltered air from passing through the ductwork while the thermostat is running.