Since the Restriction of Hazardous Substances (RoHS) directive was passed more than 10 years ago by the European Union (with many countries passing their own versions of the law), IAQ in data centers has become a major issue. That is because this directive, which restricts the use of certain hazardous substances in electronic equipment — the most significant of these being lead — has caused many types of electrical components to become much more prone to corrosion if proper air quality is not maintained.

As a result, almost all information technology (IT)/datacom manufacturers have updated their specifications, documentation, and warranty terms to include and/or update air quality specifications, said Chris Muller, technical director and global mission critical technology manager, Purafil Inc.

“These updates have almost exclusively been to require maintaining the data center environment at an ISA [International Society of Automation] Standard 71.04, ‘Environmental Conditions for Process Measurement and Control Systems: Airborne Contaminants,’ severity level of G1 for airborne chemical contaminants that can cause corrosion and/or failures of the IT/datacom equipment,” Muller said.

Dust and dirty HVAC equipment can also contribute to IAQ problems, which is why proper filtration, humidity control, and disinfection of HVAC systems are prudent strategies for any data center.


According to ISA Standard 71.04, reactivity (or corrosion) monitoring are described as the most reliable way to monitor the environment for the presence of various corrosive agents. And because of changes to manufacturers’ warranties due to RoHS, continuous real-time corrosion monitoring should be used to assure compliance, said Muller.

“Most of the contaminants responsible for damage to IT/datacom equipment have their sources outside the data center, so monitoring must be performed both inside and outside the data center,” he said.

This can be a challenging task, as many data centers have high cooling loads, so they bring in outside air — or free cooling — to minimize energy costs. However, outside air can introduce other issues, such as humidity, gaseous contaminants, and particulate matter, which can damage sensitive computer equipment.

There are solutions available, such as enthalpy sensors, which can help mitigate these issues, said Tony Moffett, executive vice president and general manager, Ruskin Rooftop Systems.

“The enthalpy sensor on the economizer measures both temperature and humidity and only activates free cooling when both metrics are in an acceptable range,” he said. “Obviously, a data center requires an ongoing clean and dust-free environment with consistent temperature and humidity levels, which is why regular inspection of incoming air filters as well as simple temperature and humidity monitoring is recommended.”

Another solution is to install proper filtration for both particulates and gaseous contaminants.


One of the biggest enemies of the electronic equipment used in data centers is dust. Even the accumulation of sub-micron size particles can develop a coating on the components, which can act as an insulator.

“This prevents the equipment from dissipating heat, which can shorten or threaten the proper operation and life of the components,” said Lynne Laake, director of marketing, Camfil USA Inc. “Our market-specific experts recommend at least a MERV-13 air filter, which is the same level used for air quality maintenance in office buildings to protect occupants.”

Gaseous contaminants, which result from the oxidation of metals and electronic components, are another concern for data center operators. This can occur due to processes within a facility or be introduced through outside ventilation air.

“In many parts of the country, ground level ozone — an oxidizer that is produced primarily from a reaction of sunlight and automotive exhaust — can induce corrosion that can threaten the transfer of data within these systems,” said Charlie Seyffer, marketing and technical materials manager, Camfil USA Inc.

In addition to ozone, acidic gases, such as  hydrogen sulfide, sulfur and nitrogen oxides, chlorine, and hydrogen fluoride; and caustic gases, including ammonia, can cause corrosion. When molecular contaminants such as these are present in data centers, gaseous contaminant removal filters should be considered.

Camfil offers two options for molecular filtration: the CamCarb cylinder system for the supply side and the City Family line of filters for recirculation. With either solution, Camfil offers ISA Check II, which tracks the degradation of the molecular media and indicates when filters need to be changed, said Trent Thiel, molecular filtration segment manager, Camfil USA Inc.

Purafil offers many filtration options as well, including the Purafilter combination chemical and particulate air filter that is installed in computer room air conditioning (CRAC) units and replaces existing particulate filters. Their Corrosive Air (CA) systems work as stand-alone recirculating air filtration systems inside data centers to clean the air and provide better air distribution.

For outdoor air, the Purafil Side Access (PSA) systems provide the higher level of air cleaning required for proper contaminant control, said Muller.

“Our air filtration solutions remove corrosive gases from the air and convert them to harmless salts that remain bound to our media,” he said. “The chemical reactions are essentially instantaneous and irreversible, ensuring complete contaminant control.”


In addition to dust and gaseous contaminants, humidity can cause serious problems not only for the equipment but for data center personnel as well.

“Where there is relative humidity above 30 percent inside the air handler, there is a chance for mold and bacteria to grow, which is a constant problem,” said Jeff Scheir, marketing and product development manager, Steril-Aire Inc. “Mold and bacteria found in the air find a home in the cooling coils of an air handler and multiply. This microbial growth often goes unnoticed until it has reached dangerous levels.”

While the growth of microbial biofilm on air-handling equipment can cause IAQ problems, it can also result in decreased cooling efficiency.

“This happens through a loss in heat transfer at the coil covered in biofilm and through increased pressure drop created by airflow blockages from the growth,” said Scheir.

The good news is that microbial buildup on data center air-handler components can effectively be removed by ultraviolet germicidal energy, said Daniel Jones, president, UV Resources. “Light in the UV-C wavelength — 253.7nm — works by disassociating molecular bonds, which in turn disinfects and disintegrates organic buildup, thereby restoring cooling capacity and airflow and increasing the potential for energy savings.”

In new HVACR equipment, UV-C keeps cooling coil surfaces, drain pans, air filters, and ducts free from organic buildup for the purpose of maintaining as-built cooling capacity, airflow conditions, and IAQ, noted Jones. In retrofit applications, UV-C eradicates organic matter that has accumulated over time and then prevents it from returning, restoring air-handler components to their as-built conditions in as little as 90 days.

UV-C works best when paired with a filtration solution to ensure that larger particles of dust and dirt are removed.

“By combining filtration with the proper UV-C solution, it is possible to eliminate the air handler as a source of IAQ issues while having an effect on contaminants brought in from the outside,” said Scheir.

It can also be a cost-effective solution, noted Jones.

“Field reports indicate that the initial cost of a UV-C system can roughly be the same as one properly performed coil-cleaning procedure and less when system shutdowns, off-hours work with the associated overtime, and/or contractor labor costs are considered,” Jones said. “As a result, it might be more rational to make a one-time investment in a UV-C system that will yield an ongoing solution.”

As can be seen, IAQ in data centers is a serious issue. Contractors who have a deep knowledge of the solutions necessary to mitigate IAQ problems, such as filters and UV lights, will be able to help their clients maintain an environment that is beneficial to both computers and humans. 

Publication date: 8/14/2017