Maximizing the life of server, storage and other electronic equipment within the data center will increase operational efficiency and add value to the organization, even though the IT equipment lifecycle may be as short as three years. UPS, servers, hard drives and other sensitive electronic equipment failures are on the increase in sites where stringent airborne contamination policies are not in place.

Data centers, from initial build to refit are dynamic environments. Critical engineering infrastructure upgrades, total equipment change-out, and even simply opening doors or entering or exiting a white space provide opportunities to introduce contaminants. These contaminants affect electronic equipment, corroding contacts and reducing capabilities to failure point, which can result in costly data center outages.

Satellite view of NO2 pollution in N Europe
Satellite view of NO2 pollution in Northern Europe – Purafil

You can’t avoid it

Many locations, which are essential for bandwidth and latency requirements of the business, are either within highly populated areas with heightened pollution levels, or on industrial parks where neighbouring businesses may generate pollutants, which then contaminate the data center

As data center owners and operators strive to improve energy-efficiency and lower carbon emissions they continue to invest in research and development driving innovation in data center environmental technologies.

The realization of ‘free-cooling’ has been intrinsic to this approach and although it is recognized direct outside air cooling can exacerbate the contamination issues due to the relatively large volumes of outside air being used to maintain the environmental conditions within the data center. The same is true, to a lesser extent, even when chilled water, condenser water and indirect outside air systems are used, as Building Regulations and Codes dictate that nominal volumes of outside air must always be provided. Even data centers located in areas without air quality concerns must plan to ensure they can maintain an environment during the life-cycle of the facility that provides protection of sensitive electronic equipment.

Corroded contacts
Corroded contacts – IBM

Humidity causes corrosion

Sites where the server environment is maintained at a high temperature must be monitored for changes in humidity, especially if fluctuations in server-load create variation in temperature. Variable humidity increases the corrosion risk, where contaminants absorb moisture and settle on electronic devices.

Equipment manufacturers have been aware of this situation for over a decade, since the European Union introduced the Restrictions on Hazardous Substances (RoHS), the lead-free manufacturing regulations for electronics equipment which came into effect in 2006. The introduction of these regulations had unintended consequences and required the use of non-lead alloys in solders, which in contaminated environments are far less resilient to deterioration.

In fact, RoHS-compliant IT and datacom equipment is at risk in locations with poor ambient air quality. In many cases, data centers in urban areas have reported UPS, server and hard disk failures caused by sulfur corrosion.

Over the past decade, ASHRAE’s Technical Committee 9.9 (TC9.9) for Mission Critical Facilities, Technology Spaces and Electronic Equipment has investigated and issued guidelines on gaseous and particulate contamination limits for data centers. These were incorporated into the update of the ISA Standard 71.04-2013 (Environmental Conditions for Process Measurement & Control Systems: Airborne Contaminants).

One of the key problems of adhering to the RoHS regulations has been that products using an immersion silver (ImAg) surface finish will corrode in environments that electronic equipment manufacturers consider to have a high sulfur content (ISA Class G2 or higher, see Table 4). This has led to manufacturers setting specific working parameters and contaminant levels for their products to remain within product warrantees.

Chemical TypesAutomobilesDiesel Engines
 Table 1 Emission factors in lb per 1000 gallons of fuel

Aldehydes (RCHO)

Carbon monoxide (CO)

Hydrocarbons (HC)

Oxides of nitrogen (NOx)

Oxides of sulfur (SOx)

Organic acids (as acetic)
















Contamination control planning

Although improving, there remains uncertainty in emissions reporting across the EU. In 2014, only half of European countries reporting the uncertainty in their emissions estimates.

This is evident in data that show motor vehicle exhaust (i.e., both petrol and diesel exhaust) in high density conurbations are up to 4X the emission level of the test-cycle emissions. Pollution from motor vehicles is a major contributor to data center contamination and examples of the primary pollutants from these sources are shown in in Tables 1 and 2.

Table 2. Emissions from diesel engines
Table 2. Emissions from diesel engines 
* CO - carbon monoxide, HC – hydrocarbons, DPM - diesel particulate matter, NOx - nitrogen oxides, SO2 - sulfur dioxide








5 – 1,500

20 - 400

0.1 - 0.25

50 - 2,500

10 - 150

In this situation, operators must develop their data center specific environmental contamination monitoring and control plan, to understand the real threat to their equipment investment. This should be included within the overall site planning, risk management, mitigation processes and improvement plan, and include:

  1. Assessment of the outdoor air and indoor environment with attention to corrosion potential. ISA Standard 71.04-2013 should be used to provide site-specific data concerning the types and level of gaseous contaminants in the corrosion being formed. An initial survey should be carried out using copper and silver corrosion classification coupons (see Image 3a – courtesy of Purafil, Inc) to establish baseline levels of total corrosion and identify individual corrosive species in the air. This information can be used to develop a contamination control strategy and determine if and what type of air cleaning may be required to eliminate the potential for damage to sensitive electronic devices.
  2. Contamination control strategy, for this to be successful it is essential to understand the chemical contaminants in the indoor environment. Then the selection of an appropriate chemical filtration system to clean both incoming air, being used for pressurization or ventilation, as well as recycled air can be effectively undertaken.
  3. Real-time environmental monitoring, based on ISA Standard 71.04 severity levels. Measurement of airborne corrosivity in a data center can be calculated using a method called ‘reactivity monitoring’. This requires the monitoring and analysis of copper and silver corrosion rates using specially prepared copper and silver sensors that correlate to ISA severity levels for equipment reliability. The use of silver reactivity monitoring as part of the assessment is required to provide a complete record of the type of corrosive chemical classes in the data center environment. This provides the data to select the appropriate filtration solution for that area.
  4. Specifically positioned real-time atmospheric corrosion monitors will provide accurate data on the performance of the chemical filtration system, if required, and allow the room air quality to be maintained, protecting the sensitive electronic systems.

ASHRAE, together with a number of computer systems manufacturers, has developed guidelines (below) to assist data center operators in implementing contamination solutions that complement equipment warrantee requirements.

Corrosion monitoring and environmental assessment

As our understanding of the consequences of airborne contaminants has grown, the industry has developed various systems and products to offer data center operators accurate, actionable and reportable data on air quality monitoring in and around the data center site. For accurate measurement, real-time atmospheric corrosion monitors (ACMs) need to be placed at specific positions around the site to discover the spread of airborne contamination. Using this data, the site operator can develop the contamination monitoring and action policy.

ISA 71.04-2013 provides a four-level classification of environmental severity for electrical and electronic systems. Referencing these levels provides a profile of potential severity of any environment, allowing preventative measures to be introduced.

 ClassSeverity Level  Copper Reactivity
 Silver Reactivity
Table 4. Classification of reactive environments
(NB these reactivity rates are in angstroms [Å] and normalized to a 30-day exposure)
 G1  Mild  <300  <200  Corrosion is not a factor in determining equipment reliability
 G2  Moderate  <1000  <1000  Corrosion effects are measurable and corrosion may not be a factor, Enig and ImmAg PCB surface finish failures
 G3  Harsh  <2000  <2000  High probability tht corrosive attack will occur. OSP and ImSn PCB surface finish failures
 GX  Svere  >2000  >2000  Only specially designed and packaged equipment to survive

It is essential to understand the individual environmental context for the data center and implement a monitoring and control solution that suits its requirements. There are many alternative solutions and the following is an outline to a successful implementation.

Working with a supplier, develop the air filtration system that meets the airflow and efficiency requirements of the data center. Consideration must be given to; controlling temperature, humidity and air purification with respect to both the current and future facility capability.

Consideration also needs to be given to the relationship between the data center’s efficiency rating and whether this equipment impacts on this process, as well as whether the system is compatible with the data center’s overall DCIM solution.

The following is best practice:

  • External and internal filtration systems should be designed to remove both particulate and gaseous contaminants. These products must be capable of being installed in or connecting to existing or new air conditioning systems, and be available in a range of sizes and filtration capabilities to match the data center’s needs. It is essential that the filter system does not impair the airflow capabilities of the HVAC system.
  • External filters must comply with air cleaning requirements for PM10, PM2.5 and ozone, and incorporate chemical filtration for contaminants specific to the site; i.e., motor vehicle exhaust, industrial activities, etc.
  • Internal filters must provide a significant amount of chemical filtration with the minimum pressure drop back into the environment. Understanding your contaminants ensures that the correct filter formulation is installed, which will maximize the systems efficiency. A large contact area is required to increase the efficiency of the filter and a parallel structure offers unobstructed airflow to ensure a low pressure drop.
  • Monitoring Systems are available that provide wireless, real-time data providing comprehensive site-wide information on a range of variants allowing trend tracking. The latest systems store and report real-time temperature, relative humidity, room pressure, along with the copper and silver corrosion severity levels. These units also provide alerts to potential failure of critical components, corresponding to ISA Standard 71.04-2013, and can prevent costly downtime and maintenance.


Contamination measurement and control has a cost, but is now a necessity due to the tightened operating specifications for today’s datacom and IT equipment. Changes in manufacturing of electrical and electronic devices brought about by RoHS and similar regulations have made this equipment more sensitive to corrosion. Couple that with the fact that the ambient air in most urban environments contains levels of sulphur and nitrogen oxides, active sulphur compounds, ozone, and/or chlorine high enough to cause significant corrosion inside the data center. With manufacturers’ warrantees demanding an ISA Class G1 environment, the use of enhanced air cleaning for outdoor air being used for ventilation and pressurization is fast becoming a necessity.

Increases in hardware failure rates due to corrosion has driven equipment manufacturers to demand that data center operators monitor the internal environment for warrantee compliance and introduce air cleaning systems as indicated by the ISA severity level to reduce the opportunity for corrosion to occur. A thorough contaminant survey and analysis ensures that the solution developed and implemented meets the specific requirements and budget. This methodology ensures that efficacy is delivered to the operator.

Best-of-breed monitoring and control systems allow a range of gaseous filtration solutions to be integrated into the data center, whether externally alongside the air-intake or internally, to monitor and purify the environment around the mission critical equipment.

Maintaining mission critical equipment at its operational level is essential to the efficiency of the data center. Allowing airborne contamination to adversely affect operational effectiveness and significantly reduce equipment life-cycles will be far more detrimental, in both equipment cost and downtime and reputation. After all, prevention is better than cure.

Paul Finch is chief operating officer at KAO Data; Chris Muller is technical director at Purafil Filtration Group