There’s a lot to consider when choosing an air filter. From understanding how an air filter works to deciphering the common terms used in the filtration industry. So, we’ve compiled the following air filter guide to help you understand what you should be looking for and find the best filter for you.
How to select the right air filter according to ISO 16890
It’s well known that making the right filter choice can substantially reduce your energy costs. The ISO 16890 has made it simple to choose the most appropriate filtration efficiency for your building. All qualifying air filters are classified from A+ to E – where A+ stands for the best energy performance and E represents the lowest. Look at our conversion from DIN EN 779:2012 to DIN EN ISO 16890 to select the most efficient air filter.
Getting what you want from your air filter
End of life
Two things spell the end for an air filter – damage and dust.
A filter can be exposed to some rough treatment throughout its life, often before it has even been installed. Air handling units are often sited in places that are awkward to reach, so filters face a lengthy – and sometimes bumpy – journey to their point of installation. And once in place in an air handling unit, variations to the air flow and incoming particulate can also damage the filter media or frame. If damage does occur, the dust-laden air can pass through the filter to the downstream application, people or equipment that you are trying to protect.
Dust may not cause such catastrophic or instant failure, but it too will eventually bring about the end of a filter’s service life. As the filter separates contaminant from the incoming air flow, the dust collects on the filter media. This dust cake blocks the air flow, causing the pressure drop – and so energy consumption – to rise rapidly. In fact, a brand-new filter will account for around 25% of the energy consumption of an air handling unit. A loaded filter increases this value to 50%. So, while it’s tempting to delay the replacement of clogged filters for as long as possible, changing too late could well cost more in the long run.
A design for life
As filter manufacturers, we focus on maximizing the life of our filters to provide the best possible value for our customers. We do this by choosing the strongest materials and combining them in the most robust construction possible. And we also lengthen service life by finding new ways to increase the dust holding capacity of our filters.
For example, we have developed special depth-loading media. Here, the media design allows the dust to penetrate deeper into the fibers instead of settling on the surface. This slows the build-up of the dust cake on the media, meaning the pressure drop remains lower for longer and overall filter life is prolonged.
Another method of maximizing dust holding capacity is how we shape the media in the filter. For example, our bag filters use pockets that are tapered towards the end. These tapered pockets load the incoming dust evenly over the entire surface of the pocket. This means the filter doesn’t become clogged as quickly as U-shaped pockets, which feed the air through the end of the pocket only.
It’s the most obvious cost, but it’s sometimes difficult to make a like-for-like comparison when judging competing air filters. Two filters that appear similar on paper – same size, filter class and other options – can perform very differently over their service life. These performance disparities can occur from differences that lie beneath the surface in the media technology and other elements of filter design. You can explore these differences in more detail in our SlideShare – the mechanics of air filtration.
Breakdown of the lifecycle costs of an HVAC air filter. It has no power cable or batteries, so it may seem strange to talk of the energy consumption of an air filter. But a filter consumes energy thanks to the resistance that it causes to the air flow in the HVAC system. The higher this resistance – or pressure drop – the harder the fan has to work to shift the same volume of air.
This energy consumption is by far and away the highest cost associated with an air filter. Eurovent – the European Association of Air Handling and Refrigerating Equipment Manufacturers – found that 80% of a filter’s total cost of ownership comes down to energy consumption. In comparison, the purchase price accounted for just 10%. That’s why a filter with a cheaper purchase price may well end up costing much more in the long run. To put that further into perspective, air filters account for 15% of the energy use in the average commercial building.
We’ve yet to perfect self-installing filters, so you will still need at least one person to fit filter elements into your air handling unit. Once in place, an air filter will need periodic inspection to ensure it is in good condition, and occasional cleaning to remove any larger debris or dust. Whether these jobs are carried out by an employee or external service provider, there will be a cost associated with that work.
Outside of specialized applications, such as biological research or the nuclear industry, most air filters are relatively straightforward to dispose of once they reach the end of their service life. But it can still be an expensive business; disposing of an HVAC filter typically costs around a third of its purchase price and products with a glass fiber media can be even more costly. These products have to go to landfill – as they cannot be incinerated – and are more difficult to change due to the health and safety risk to the service team.
An HVAC air filter typically serves two purposes – to protect the other components of the air delivery system from dirt and damage, and to provide clean and fresh air for people in the building. There may be other niche applications, such as protecting artefacts in museums, but generally the aim of an air filter in commercial buildings is to protect the health of people and/or equipment.
To do that, an air filter needs to capture contaminant from the incoming air flow. Different filters will perform this function to different levels depending on their size, shape and design. But ultimately, a filter’s stopping power comes down to filtration efficiency. The greater the number and smaller the size of particles that a filter can separate, the higher the filtration efficiency.
In the days of the EN779 standard, F7 was the go-to filtration class for HVAC air filters. We now have a new standard in ISO 16890, but you may well still have an F7 in your air handling unit. There’s potentially nothing wrong with that. But have you ever reviewed your filter system to determine if it’s delivering the outcome that you wanted when you bought your air filter? If not, you are far from alone. But more and more companies are taking a different approach to filter purchasing – one that is based on delivering the standard of clean air that they need.
Maximizing life and value
- Stop watching the clock: Many filters are replaced after a set period – such as six months or a year, typically when the service team makes its scheduled visit. But this rigid approach does not take into account the performance of different filters and the various environments in which they operate. Over a set period, the filters in one building may be loaded to the brim with dust, while another set of filters is virtually clean. It all depends on the level of incoming particulate and the capabilities of the installed filters. So, make checking the system pressure drop part of the regular maintenance routine. If the filter has exceeded its recommended final pressure drop, it’s time to change. And when looking for replacements, choose filters that are suitable for the level of incoming particulate. Our eco16 Filter Management program can help you find the right filter for your individual operating environment.
- Look for robustness: A broken filter is little use to anyone, so conduct regular visual inspections of your filters to identify damage before it causes further issues. When replacing filters, look for design features that add robustness to the filter. Plastic or metal frames are usually preferable to cardboard. Grids or guards can help protect the media. And simple additions like carry handles can stop the filter becoming damaged during installation and lengthen its service life accordingly.
- Check the capacity: Most manufacturers will detail the dust holding capacity of their filters in the product literature. If they do not, ask them for the data. An air filter with a higher dust holding capacity is the simplest way to maximize the life of your filter system and minimize your costs.
- Focus on lowering energy consumption: Reducing the energy consumption of an air filter comes down to lessening the resistance that it causes to the air flow. If we reduce the pressure drop, we can adjust the fan or reset the inverter to consume less energy. To simplify the task of searching for an energy efficient air filter, Eurovent and its participating members run an energy rating scheme. Just like a television or refrigerator, qualifying products are rated on a scale of A+ (the best) to E (the worst). For products that fall outside the scheme – such as filters that offer lower and higher levels of air cleanliness – look for a lower pressure drop to minimize your energy spend. It will be around 80% of the total cost that you spend on a filter, so it’s worth considering carefully.
- Choose a longer life: The longer your filter lasts, the longer you can delay spending out on installation, disposal and servicing costs. So, look for products that offer a longer service life – typically those with a higher dust holding capacity.
- Look for eco (and wallet) friendly disposal: The best way to dispose of your used filters is by incineration, which provides energy recovery as well as reducing landfill. But filters with a metal frame and glass fiber media cannot be disposed of this way. So, look for filters with plastic frame and a synthetic media to reduce your disposal costs and lessen the impact on the environment.
Filters must perform in all kinds of settings – from cool and wet cities to dry and hot rural environments. The type and size of contaminant that filters face will vary drastically from location to location, as will the humidity, temperature, air flow and other factors that influence filter performance. In fact, the operating environment and pollutant type will often vary between neighboring buildings. That is why a one-size-fits-all approach to filter selection can compromise air quality and put at risk the things that you are trying to protect. An outcome-based approach that uses hard evidence on the operating environment and your goals, can ensure the safety of the people and equipment in your building – and save you money too. Here’s how it works.
- Decide on an outcome: The most likely reason for installing HVAC filters is to protect people and components. Us humans are the most vulnerable and valuable of those two categories, and if it’s safe for people, it’s safe for the rest of the HVAC system. So, your desired outcome for your filtration system will be to provide safe air quality for the occupants of your building. Fortunately, the World Health Organization (WHO) tells us exactly what this safe level is: 20 mg/m³ for PM10 (particulate less than 10 µm in diameter), and 10 mg/m³ for PM2.5 (particles smaller than 2.5 µm).
- Find out what you’re up against: Now we know the outcome that we want, we need to determine the levels of the incoming contaminants. Most countries around the world now publish pollution levels across their regions – often with detailed historical records and sometimes in near real-time. So, finding out the levels of PM10 and PM2.5 in your local area can be a quick web search away.
- Do some sums: Armed with the local pollution levels you can then calculate what filtration efficiency will remove enough of the contaminant to deliver a safe level of air quality. For example, if the PM concentrations outside your building are 48 μg/m³ for PM10 and 33 μg/m³ for PM2.5, you need a filter system that can reduce PM10 by 58% and PM2.5 by 69%. This equates to minimum ISO 16890 filter efficiencies of ePM10 60% and ePM2.5 70%.
- Use a safety buffer or survey: Of course, the published air pollution levels will not give you a precise picture of your individual building. Pollution levels are far from static, and localized pollution caused by construction or industrial activity can be missed in regional published data. So, we recommend adding a safety buffer and choosing a filter 10 - 20% cleaner than your calculations may suggest. This will cover any periods of high pollution and mitigate the risk from neighborhood sources. Better still, ask your filtration partner to conduct an air quality survey of your building. We regularly analyze customer sites as part of our eco16 program. We measure the incoming level and type of pollutants, and create a tailored filter solution that guarantees safe air quality at the lowest possible cost. Find out more about eco16 here.
- Watch out for over-specified filters: At this point you may be asking yourself why not just choose the highest filtration efficiency possible. And the answer comes down to cost. Higher efficiency filters tend to be more expensive to buy and – as they are designed to trap finer particles – will load with coarse dust much more quickly than lower class filters, shortening the operating life considerably. But the biggest cost implication of over-specifying filter efficiency comes down to energy consumption. A filter that has too high a filter class will choke the air flow and cause the energy consumption of the whole HVAC system to soar.