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Not all air filters have the same quality and efficiency that we need. In the market, there are alternatives that adapt to each user, but not everyone knows how to qualify these options. When we see a MERV rating filter, we may not know what the acronym they have means, which makes us doubt whether it is the right purchase.

Today we will help you understand the MERV ratings so you can choose the one you need in your home or business.

What does MERV mean?

merv What MERV rating filter should I use and why

MERV stands for Minimum Efficiency Reporting Value. This is the standard that determines the quality of an air filter. Through a numerical system, the quantity of particles that an air filter lets through is qualified.

The highest the MERV rating, the higher the amount of dust, pollen, mold, bacteria and smoke particles that a filter prevents from passing. Depending on the device for which we need the air filter, the MERV rating will change.

What is the function of the MERV rating?

merv1 What MERV rating filter should I use and why

Before the existence of the MERV rating, determining the efficiency of an air filter was complex. With the creation of the MERV rating, there was finally a way of knowing when a product met parameters to be considered better in its function.

The American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) coined the term in 1987. MERV ratings are an easy way to determine if an air filter is suitable for certain buildings such as hospitals.

MERV rating chart – Where to use the corresponding filter

merv2 What MERV rating filter should I use and why

The MERV chart consists of a table that classifies filters with a number from 1 to 20. The higher the number, the greater its efficiency. In general, a filter of category greater than 16 is only found in health centers, nuclear plants and other types of spaces that require a sterile environment.

MERV from 1 to 4 – Fair protection

merv4 What MERV rating filter should I use and why

The first four MERV categories are intended for basic filters that only protect against the most prominent dirt. Although they will trap 80% of the particles of 50 microns or more, it is only 25% effective against those of lower measurements.

These filters tend to be disposable and cheap, and they do not resist prolonged use, having an average useful life of one month. They are excellent for protecting the equipment that uses them, such as motors and fans, but they do not work to purify the air.

MERV from 5 to 8 – Improvement for health

merv8 What MERV rating filter should I use and why

Starting from this range, the filters have a positive effect on health. Since they are capable of removing up to 95% of the particles that pass through them, agents such as mold or aerosols will be filtered until they are removed.

MERV rating filters of this category can cost up to 4 times more than those of the previous levels, but it is due to the quality of the materials and the pleat of between one and two inches that creates more layers. These are ideal for homes and businesses.

MERV from 9 to 12 – The standard option

merv11 What MERV rating filter should I use and why

The filters that fall between these categories offer the best possible protection for homes. These are essential for people with respiratory problems.

The manufacture of these filters is very complex, including a large number of pleats to achieve the best air purification for domestic use. They are so efficient that they absorb virtually any residue from the air, which causes them to get dirty quickly.

We will have to clean our heating, air conditioning, and air purifiers systems with some regularity if we decide to use a MERV rating filter of this category.

MERV from 13 to 16 – The major leagues

merv16 What MERV rating filter should I use and why

The categories above MERV 13 are used by hospitals and other places that need to purify the air to the fullest. They are not made for residential use since the domestic cooling or heating equipment needs some airflow to function properly, and these filters restrict it, which can damage them.

MERV from 17 to 20 – Exclusive use

merv17-20 What MERV rating filter should I use and why

This range is designed for the areas with the highest sterilization in the world. They will only be found in pharmaceutical development companies and electronics factories.

MERV rating filter ideal for our home

As we mentioned, a filter with a high MERV rating means that it gives us better air purification. However, this also increases costs and many times that additional efficiency is not necessary, besides that it can be harmful to some devices.

For residential use, it is best to purchase filters between the range 4 and 12. The optimum are MERV filters rating 7 and 8, as they offer a value for money adapted to most users.

In case our budget is limited, the MERV 4 is the minimum recommended, although this will not be useful to purify the air. If we need a filter for a special air purification device for a person with allergic or respiratory problems, then we should make the effort to get a type 11 or 12 filter.

Examples of optimal filter selections

Unit with up to two members: in general, domestic units with one or two people will have all members of the household working for a good part of the day, so the house does not need a filter that works all day.

If additionally, they do not have pets, they clean constantly, and they do not smoke, then the air will be kept clean naturally, so a MERV rating filter greater than 8 is not necessary.

Unit with up to five members: groups from two to five people tend to be families with young children. These will require additional care, especially during early age. You are also likely to start receiving your children’s friends, which will generate more dirt. A category 11 filter would be optimal.

Unit with six or more members: statistically, some of the people in the largest families likely suffer from respiratory problems, whether due to an allergy or old age. As there are more people within a space, there are also more germs, which merits deeper filtering. A MERV 12 filter should not be missing in our home.

Elements to consider about air filters

Pressure drop

HVAC-Filters What MERV rating filter should I use and why

This phenomenon occurs in all systems that have an air filter. This translates as a decrease in the amount of air that reaches a place.

In this case, because the filter slows and controls the amount of air that passes, the vents of your HVAC will always have some pressure drop. The higher the MERV rating of the filter, the greater the pressure drop in your system

How does the pressure drop affect your filter choice?

How-does-the-pressure-drop-affect-your-filter-choice What MERV rating filter should I use and why

Since not all equipment has the same power or capacity to filter the air, a very high pressure drop could damage them. Domestic fans and motors are not designed for filters that drastically limit airflow, so a higher MERV index will not improve our experience with them.

It could even make air quality worse by compromising your health. Check the product manual before changing the filter.

Remember the constant maintenance

hvac-filter-change What MERV rating filter should I use and why

The higher the MERV rating, the more waste they will accumulate. As a result, we must change them more consistently than those with a low MERV rating.

A filter with tiny pores will be blocked more easily, making it difficult for air to flow freely, and this will increase the pressure drop, creating a risk for your HVAC equipment.

The manufacturers’ recommendation is to replace the air filter every 3 months for the lower ranges. A MERV rating filter higher than 8 should be replaced every 2 months so as not to wait until the extreme situation of forcing the equipment.

Each device needs a different filter

Now that you know what the MERV rating is, you can make a better decision when changing the air filters. Each HVAC works differently, so you should always refer to the manufacturer’s recommendations to determine the best filter.

Remember that it does not always require a filter with a high purification level. You can save a considerable amount of money if you do not need totally clean air.

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