It's Time To Learn More About Humidity

Have you seen the FDA’s web site home page recently —

Here are some other recent headlines to consider:

September 2, 2010 (Source: U.S. Department of Commerce, National Oceanic and Atmospheric Administration)

“We expect El Niño to strengthen and persist through the winter months, providing clues as to what the weather will be like during the period,” says Mike Halpert, deputy director of the Climate Prediction Center — a division of the National Weather Service. “Warmer ocean water in the equatorial Pacific shifts the patterns of tropical rainfall that in turn change the strength and position of the jet stream and storms over the Pacific Ocean and the U.S.”

And from the NASA Goddard Institute of Space Studies July 2010 report entitled, “GISS Surface Temperature Analysis — What Global Warming Looks Like”:

“What we can say is that global warming has an effect on the probability and intensity of extreme events. This is true for precipitation as well as temperature, because the amount of water vapor that the air carries is a strong function of temperature. So the frequency of extremely heavy rain and floods increases as global warming increases. But at times and places of drought, global warming can increase the extremity of temperature and associated events such as forest fires.”

While these and similar reports might give anyone pause, they should instead compel pharmaceutical quality managers to action.  The unpredictable and erratic weather patterns that are widely reported in North America as well as around the globe may mean that longstanding environmental controls may now be — seemingly suddenly — inadequate for the controlled environments that product quality and regulatory compliance require. 

Erratic weather, from a monitoring standpoint, is often a reason why pharmaceutical and other medical product warehouses find themselves in trouble. The fix may require building modifications, new conditioning equipment, and/or changed practices. It also requires mapping of any compliant spaces being altered and monitoring after the changes are in place. Many of the largest pharmaceutical and medical product distributors have long grappled with this problem because they have multiple warehouse facilities across the United States in very disparate climates, and with newer facilities often equipped with state-of-the-art environmental control systems while older ones have less up-to-date control systems or are in transition. (For an example of how one of the largest medical surgical suppliers to the acute care market in the country proactively took control of their environmental monitoring systems BEFORE they became non-compliant or compromised product quality, see a report on Owens & Minor.)

From the viewpoint of Veriteq, now a Vaisala company, which arguably invests more R&D dollars to assure the highest accuracy sensor technology for critical environments, there are very real reasons why controlling and monitoring humidity is more challenging than some may think.  It’s an immutable law of metrology: all sensors drift. Humidity sensors are uniquely prone to drift however, for the simple reason that they’re “air breathers.” Unlike temperature sensors, humidity sensors must be in direct contact with the environment.

Not only is the air constantly changing temperature, which affects RH, (even without the nuisance of unpredictable weather patterns!), but it also contains contaminants that can affect humidity any sensor. Unlike temperature sensors, the internal structure of the RH sensor has no protective barrier from airborne elements, so the sensor’s ability to measure degrades over time, and especially if quality-by-design principles were not at work by the engineering teams creating the humidity monitoring system. 

Understanding how humidity measurement devices function can mean the difference between purchasing an instrument or system with inherent measurement flaws and getting one that measures accurately between calibrations.  The ability to understand humidity measurements in greater depth will allow you to select a system that can best help with meeting your quality system requirements and regulations.  Whether your facility is facing more storm clouds or droughts, it is “back to school” season for anyone in the pharmaceutical industry that wants to ensure that their working knowledge of humidity is up to the challenges — environmental and enforcement — of our time.  No need to travel far.  

Vaisala’s Humidity 101 Webinars have been attended by thousands worldwide and are a click away from your desktop ( If you prefer face-to-face seminars as your study method there are likely ones being held near you sometime soon.Visit if you would like to register yourself or other team members for a Humidity refresher course that not only reviews general scientific principles but also discusses the regulatory aspects of humidity monitoring and where current FDA inspections are finding quality discrepancies.