Tiny particulates are the enemy of data center operators. If left unchecked, dirt, dust, and pollen can accumulate on IT equipment and cause it to run inefficiently, corrode and, in some cases, critically malfunction.

Luckily, help is at hand in the form of filters, which can intercept these particles - as well as potentially damaging gases - as air is circulated around data halls by their cooling systems.

Given that their job is to catch dirt, these filters naturally have a limited shelf life, and thousands are thrown away each year, adding to the sizeable carbon footprints that most data center operators are actively seeking to reduce.

Could a reusable version be a better option? Filtration specialist K&N Global certainly thinks so, having worked with Apple to develop a washable filter that it says can last for years. The filter has helped Apple make significant savings in its data centers, and now the product is apparently being eyed by other operators, too.

Finding your filter

Data center air filters can be made from a wide variety of synthetic materials designed to resist moisture or microbial growth.

Their effectiveness is measured in minimum efficiency reporting value, or MERVs, with the MERV value reflecting the size and type of particles they can trap. For air-cooled or partially air-cooled data centers using computer room air conditioning and computer room air handlers, MERV 8, 11, or 13 filters are typically used, though some operators may turn to high-efficiency particulate air, or HEPA, filters, which can catch very small particles and have a MERV score of 20.

Traditional filters are changed three or four times a year, depending on the environment a data center is running in. This means a large amount are being sent to landfill; K&N claims its analysis shows that a 100MW data center, of the type now being regularly constructed by the hyperscalers and the companies courting their business, gets through enough air filters to cover three football pitches annually, some 225,000 sq ft (2,100 sqm). When metal components and packaging as well as the filter material itself are factored in, the US data center industry is apparently sending 60,000 tons of filter waste to landfills every year.

K&N has been making filters since 1969, but its foray into data centers is much more recent. The company was founded by two motorcycle racers, Ken Johnson and Norm McDonald, both of whom have been inducted into the American Motorcyclist Association Hall of Fame for their exploits on - and off - the track. Having met through the sport, Johnson and McDonald teamed up to initially open a chain of motorcycle repair shops in California, but soon turned their hand to engineering parts, too. Together, they designed the High-Flow Air Filter, a novel type of filter that allowed more air to reach a bike’s engine.

“Back then the amount of power of an engine was directly related to the amount of air it could ‘breathe,’” says Jason DiFuccia, product leader at K&N Global Filtration. “So they came up with this filter to help them become better racers, and we’ve become the leader when it comes to all things performance air filter-related.”

Indeed, K&N’s products were hailed as revolutionary when they first hit the market, and are now widely used by racers looking for a performance boost. The company has continued to innovate, and has been marketing a reusable automotive air filter for some years, which is how it caught the attention of Apple.

Reuse in the data center

Though conceptually similar to the reusable filters designed for engines, K&N’s data center filter is an entirely new product, DiFuccia says. The in-engine version is made of a cotton-based material, which means it has to be reoiled every time it is washed to maintain its efficiency. “We don’t want to be oiling up filters that go in a V-Bank by the thousand,” DiFuccia says. “So the ones being used in data centers are a dry media, a synthetic material that doesn’t require any oiling or indeed any chemicals in the washing and reusing process.”

Though DiFuccia doesn’t go into detail about what sort of material makes up the filter, he explains that it traps dust and other particles on its surface, rather than within its weave in the way that a cotton filter would, making it easier to clean. K&N says the filter is the only product of its kind on the market, though other non-data-center-specific reusable filters for industrial settings are available.

Its design has been honed through the partnership with Apple, which contacted the company back in 2019 with the aim of developing a reusable filter that it could use at its growing estate of data centers.

The product was first installed at Apple’s campus in Reno, Nevada, with more than 20 iterations of the filter built and tested before the final version was settled upon. It has now been rolled out across the iPhone maker’s five US data centers, and is available to purchase by other operators in both V-Bank and Panel cooling system designs. Versions with MERV ratings of 8, 11, 13, and 14 are currently on the market, and DiFuccia claims it is easy to customize the design to meet the environmental requirements of a particular data center or client.

Of the partnership with Apple, DiFuccia says: “They’ve been very involved from the beginning, and they’ve had an open door for us if we’ve needed to come in and measure, test or prototype, and very forthcoming in terms of supplying test data and what could be improved.”

He adds: “Reusable filters have been tried in data centers before but they haven’t been able to prove themselves out from a washing protocol or return on investment perspective. This is the first one I’m aware of that has a real-world application in the data center space, and for us it’s wonderful to be able to say we have a solution which is in use by a big company like Apple.”

Making a splash

Apple says the filters are making a tangible difference to its emissions, and claimed in its most recent sustainability report that they have helped it avoid sending 25 tons of used filters to landfill a year. It also says it has cut fan energy use by 35 percent with the devices.

K&N says its filters last 15 years, and has conducted a life cycle analysis of the product which has not yet been published but apparently shows big carbon footprint benefits. “The comparison is one of our filters to 15 years worth of disposable ones,” DiFuccia says. “The reduction of carbon, the reduction of energy, and the reduction of water use is significant.”

The filters can be washed using a standard hose with cold, low-pressure water, and can come clean in 30-90 seconds, DiFuccia says, though this process can take longer depending on what’s in the air. “From a sustainability perspective, it’s about as light as we can make it,” he adds.

DiFuccia says K&N is looking at further uses for its filters in the data center, and though the company’s focus remains largely on its automotive business, tackling a new vertical has been a refreshing challenge for its team of engineers. “It’s pumped a lot of lifeblood back into the veins of the business,” he says.