How to Replace an HVAC Filter Correctly

Changing an HVAC filter is simple, but installing the wrong size or reversing airflow direction can reduce performance. The existing filter and the equipment label usually provide the information you need.

Tools you will probably need

• usually none
• flashlight if the filter slot is dim

Materials

• correct-size replacement filter

Project steps

1. Turn the system off at the thermostat while you access the filter.
2. Remove the old filter and note its exact dimensions and the airflow arrow direction.
3. Insert the replacement so its airflow arrow points toward the blower or air handler.
4. Close the filter cover securely and restart the system.

Common mistakes

• Guessing at filter size
• Installing the airflow arrow backward
• Choosing an extremely restrictive filter without considering the system

When to call someone

Ask an HVAC professional if you cannot locate the filter, the system uses a specialized media cabinet, filters collapse or become unusually dirty very quickly, or airflow is poor after replacement.

Project costs and times are rough planning estimates. Product instructions, local codes, home construction, and actual conditions take priority.