You’ve probably been told to replace your furnace filter every month to every three months or follow the manufacturer’s recommendations. These suggestions are fine, but may be wasteful. Here are a few things to think about when purchasing, replacing and inspecting your furnace filters:

• Pleated Vs. fiberglass. Pleated filters cost slightly more than standard fiberglass filters but are much more effective at removing particles because there’s more surface area for the air to pass through. Pleated filters use a MERV (Minimum Efficiency Reporting Value) rating. The higher the MERV rating, the smaller the particles it will filter. 
• Life of a filter. The longer a filter is in place, the more efficiently it removes particles. On the reverse side of that coin, it also slows or stops air flow. That is why it is important to get a filter that removes the particles you want to eliminate and still allow air flow. That is also why it is important to inspect the filter periodically.
• Time to inspect. When inspecting your filter, you want to look for the buildup of debris. Debris is very easy to spot on fiberglass filters. It typically looks like grey or light brown snow and stands out in contrast to the (usually colorful) fiberglass. On pleated filters, you want to look in between the pleats for the buildup of debris. If you hold the filter up to a lightbulb and can’t see light through the debris, then it is time to change your filter. 
• Err on the side of caution. It’s not going to hurt to change your filter if you’re not sure if it will last longer. In contrast, if you leave a filter in too long, it can drastically reduce or stop air flow, which can create all sorts of trouble.

As always, I’m here to help. If you have questions or need me to look into anything, give me a call.