An interesting Twitter account to view or follow is @BeijingAir, a Twitter handle owned by the U.S. Department of State that posts air quality data for five cities in China among others. Hourly Tweets keep followers informed about the air quality in Beijing.
Recent data has been both alarming and amazing. The data shows air quality at 524 for PM2.5. This reading describes the micrograms per cubic meter of particles 2.5 microns (0.0001 inch) or smaller in size. The 524 reading in the topmost tweet means 525 very small particles are found in every cubic meter of air (35 cubic feet or 262 gallons).
U.S. Environmental Protection Agency (EPA) diagram demonstrating PM 2.5 and PM 10 sizes
U.S. Environmental Protection Agency (EPA) PM 2.5 designations
While this does not seem like a lot, the EPA designates PM 2.5 from 301-500 as Hazardous to breathe. A PM 2.5 level of 524 is off the scale. That can’t be good. Most of these fine particles are the products of combustion, primarily motor vehicles, power plants primarily those burning coal, or wood fires used for heating. Beijing’s air has been so bad recently it has made national and worldwide headlines. These small particles can pass deep into the lungs; regular or continuous exposure can lead to lung damage or disease.
Early December 2015 headlines noted China issued a Red Alert for Beijing, the first time such an alert has been issued since the early air pollution alert system was announced in 2013. The Red Alert was issued as a forecast that PM 2.5 would be above 200, Very Unhealthy based on the U.S. EPA table, for 72 hours, or 3 days. The Red Alert meant schools will be closed, cars will be able to drive only alternate days based on license plate numbers, and fireworks and outdoor barbeques are banned. The government reduced its car usage by 30% during this emergency. Many residents wore filter masks to minimize the hazard.
Smog from power plants and motor vehicles led to Red Alert days in Beijing in December 2015
What does all this have to do with data centers. A July 2015 post in Data Center Knowledge headlined that Pollution in China Makes Free Cooling Difficult for Baidu. The piece noted, “Air pollution in China has resulted in higher IT equipment failure rates for Baidu, the internet giant that’s the country’s answer to Google.” While companies like Baidu may attempt to reduce their energy usage using “free cooling”, air-side economizers, corrosive gases generated with the soot corrode exposed electronics. Deploying air-side cooling in such environments requires not only added particulate filtration but attention to corrosive gases.
To make matters worse, particulate matter, the product of combustion, is essentially carbon, a very efficient adsorber. Corrosive gases such as sulfur dioxide (SO2) and acidic oxides of nitrogen are adsorbed onto the soot and delivered with the particle into the server rack. These two gases are primarily responsible for the “acid rain” that made national headlines in the U.S. in the 1990s and led to Congress passing new, lower emission standards for coal fired power plants.
Server manufacturers often specify MERV 11 or MERV 13 filters for data center clean rooms. Even with this level of filtration, one-quarter to one-third of PM 2.5 will penetrate MERV 8 and one-tenth of PM 2.5 will pass through MERV 13 filters. With high levels of particle contamination from the outside air continuously challenging these filters, the amount of particulate matter with adsorbed corrosive gases is substantial. Since carbon is only adsorbing the corrosive gases, they can desorb when the end up on circuit boards and connectors, becoming concentrated sources and challenging even the most diligent data centers corrosion prevention strategies.
Most U.S. data center operators are not facing such daunting challenges today. Locating data centers outside of major urban centers adds an additional level of protection, so long as the data center is not downwind of a U.S. midwest coal fired power plant levels should be low. Data center operators employing “free cooling” strategies in the U.S. will likely not face the challenges of coastal China sites any time soon. In the meantime, in addition to humidity and temperature, real-time monitoring of air quality outside and inside the data center is relatively inexpensive and will allow operators to build a baseline from which to examine future data. Also of concern are non-obvious sources of corrosive gases or particulate matter such as fertilizers or dust that can travel long distances. And reports of air pollution from China making its way to the U.S. are becoming more frequent. At the least, monitoring ambient particle levels will provide some insight to the level and efficiency of HVAC intake filtration and help facilities personnel keep on top of potential issues.
Many data center operators in China take additional measures such as corrosive gas filtration or intake air scrubbing to reduce corrosive gas levels entering the site HVAC system. These measures are not without cost and require regular recharging or maintenance. U.S. data centers have for the most part enjoyed freedom from corrosive gas corrosion; those associated with chemical plants or paper mills being two notable exceptions. Continuous monitoring of corrosive gas and particle levels in addition to temperature and humidity is not commonly done in the U.S. And data center electronics suppliers are continuously working to improve their product’s corrosion resistance. However, while lead-free electronics initiatives have helped with health issues, they have put modern electronics at greater risk. Before the world was connected globally by economics and trade, it was connected globally by the air we breathe and the water we drink. Having a baseline from which decisions can be made is good practice regardless of the location, whether Beijing, Boise, Brussels or Boston.