These results may be cause for some concern among anyone worried about server uptime: As you can see, the failure rates are relatively low across the board -- but the servers in the air-side economization trailer failed nearly twice as much as those in the room where traditional cooling was employed. On the other hand, it's notable that Intel made the conditions in the "free cooling" section unusually harsh.
Intel is certainly not dismissing the potential ill-effects of outside air on the machines entirely. "We plan to further test for possible hardware degradation using a server-aging analysis that compares systems used in the economizer compartment, in the air-conditioned compartment, and in our main datacenter," Intel reports.
One remedy to the problems posed by humidity and contaminants could be ruggedized chasses, such as the IBM BladeCenter T and HT. As described by Big Blue, these chasses comply with both NEBS (Network Equipment-Building System) Level 3 and ETSI (European Telecommunications Standards Institute) standards and are "ideal harsh environments and running applications under the most demanding conditions." The hardened design "enables performance across broader range of temperatures and humidity," according to Alex Yost, VP for IBM BladeCenter at IBM, and "enables airborne contaminant filtration" to boot.
One of these chasses, loaded, would run around $5,000 more than a standard chassis, according to Yost. Still, it amounts to a smart investment if you're contemplating exposing your machines to free outside air under harsher-than-normal conditions.
You can download Intel's white paper on its air-economizer experiment, titled "Reducing Data Center Cost with an Air Economizer"; there's also a video available on how the air economizer works.