One of the most common mistakes homeowners make is installing their furnace filter backward, restricting airflow and hindering its effectiveness. In this guide, we'll clear up any confusion surrounding furnace filter direction and show you how to install yours correctly. Key Takeaways: Arrow Direction: The arrow on your furnace filter should always point towards the furnace, indicating the direction of airflow. No Arrow? No Problem: Use the wire mesh or (carefully) feel the air methods to determine airflow direction if your filter lacks an arrow. Regular Replacement: Change your filter every 1-3 months for optimal performance and air quality. Correct Size: Use the correct size filter to prevent gaps and ensure proper filtration. Table of Contents Decoding the Arrows on Your Furnace Filter Determining Air Flow Direction Without an Arrow Common Furnace Filter Mistakes and How to Avoid Them Decoding the Arrows on Your Furnace Filter Most furnace filters have an a...