QThere are a lot of filters on the market. How do I compare the different brands? There are several ways to compare filters including arrestance, efficiency, dust loading capacity, and MERV rating. After being in the filter business for many years, we believe the Minimum Efficiency Reporting Value or MERV is the best standard of comparison. The air filter industry is governed by the American Society of Heating, Refrigeration and Air conditioning Engineers or ASHRAE. The MERV standard or filter test method was developed by ASHRAE and is the best means for an "apples to apples" comparison of filters. This is the method used by engineers in industrial and commercial applications, in other words, the people that use filters every day. This is why the MERV rating is listed for every style of filter we sell. The higher the MERV rating the more dirt particles in the air the filter will trap.   QHow do I choose a filter that's right for me? If you are shopping at our site, you are probably looking for a better filter than what is available at the local store. Or you are using a high quality filter and have found we are a less expensive source for the product. It makes sense to use the highest MERV rated filter you can afford. The higher the MERV rating, the cleaner your heating or air conditioning system will remain. The cleaner it is, the more efficient it operates. The more efficient it operates, the lower your utility bill. Further, the higher the MERV rating, the less particulates in the air leaving the filter. Having said this, we are all limited in our filter choices by the ability of our unit to pull the air through the filter. In general terms, the higher the MERV rating the more power it takes to pull the air through the filter. If the fan in our unit can't pull the air through the filter, we need a filter with lower resistance. If you have an older unit in your home, older than 10 years, you should probably stick with a MERV rated filter of 8 or less. Remember a MERV 8 filter is still 200% better than the fiberglass panel filters used in many homes. If you have a new unit, you may want to try a MERV 11 filter.   QHow often should I change my filter? This is a good question that is tough to answer. On average many users change their filter every 30 days. However, how many hours the unit has been running per day is much more important than how many days the filter has been in it. As your air filter loads with dirt, it becomes harder for the fan in your unit to move air through the filter. If you notice a decrease in the amount of return air from your unit, the filter may need changed. Or if you see a substantial change in the color of the filter media it may need changed. We change the filters in our home often and believe it helps keep our home clean.   QDust sometimes collects on the air duct screen. Is something wrong with my system? The fan in your unit pulls air towards and through your filter. As the air approaches the filter, its velocity slows and some particles may fall out. This can cause dirt to gather around the air duct screen or grill. In most cases there is nothing wrong with the filter. However, as your filter loads with dirt, it becomes harder for your unit to pull the air through the filter and thus the air slows down even more. In many cases this is when we see the grill begin to collect dirt and this is a sign to change your filter.   QI see filters labeled with a MERV rating. What does that mean? MERV stands for Minimum Efficiency Reporting Value. The air filter industry is governed by the American Society of Heating, Refrigeration and Air conditioning Engineers or ASHRAE. The MERV standard or filter test method was developed by ASHRAE and is the best means for an "apples to apples" comparison of filters.   QAre permanent air filters better at keeping the air in my home clean? As we stated previously, the MERV rating is the best means of comparing filters. If an electrostatic or permanent filter has a high MERV rating it may be a good choice. Of course, you have to clean the filter often and many times water is used to help get the filter clean. We bring this up because moisture in an air filter is not a good idea. When filter media gets wet, there is a chance mold, fungus or bacteria could begin to grow on it. It doesn't happen all the time, but it is a possibility. We have tried several "permanent" filters over the years and have always come back to pleated filters that we can simply throw away when they are dirty. Q The filter size I need is not available here. Can you make a custom size? Yes, we can make any size filter you need up to a 25"x35" in our MERV 8 pleat or our MERV 4 panel filter. If either of your dimensions exceed one of these, simply divide your largest dimension by 2. In other words if your opening is 24x50, order filters that are 24x25 and use two at a time. Click here for more information on custom sizes.