By Duncan Curd
To understand the importance of controlling relative humidity levels within the complex environment of a laboratory or cleanroom, it helps to know that the term humidity simply refers to the amount of water vapor in the air and is measured in terms of relative humidity (RH). Relative humidity is a function of both moisture content and temperature. It describes the actual amount of water vapor in the air as a percentage of the maximum amount of water vapor which the air could hold at a given temperature.
Issues Caused By Low Or Fluctuating RH
The prevention of contamination is of primary concern in a laboratory or cleanroom since the potential for the growth of microbes and bacteria increases in an improperly controlled environment. The high rate of air changes needed to control the air quality and keep these areas sterile can cause low or fluctuating RH levels, which in turn causes problems with equipment, chemicals, and measurements.
Static electricity discharges caused by low or fluctuating RH levels can damage valuable equipment and disrupt critical processes. When humidity levels are lower than 45% RH, equipment may experience static buildup which can cause materials to dry out and become brittle. In pharmaceutical manufacturing, there may also be issues during the tablet pressing and packaging stage as excessive static causes medicine to stick together. Too much humidity creates an ideal environment for viruses, bacteria, and mold to grow, compromising the integrity of the pharmaceutical drug. The ASHRAE¹ Handbook recommends that laboratory and cleanroom facilities maintain the relative humidity level between 35 – 60 % RH.
Relative humidity levels that are too high or too low can interfere with test results. Whether from a brief interval when an HVAC system starts up or from season changes, the slightest fluctuation in humidity can affect the accuracy of sensitive testing. In an uncontrolled environment the life span of expensive equipment such as spectrometers and electronic microscopes can be notably reduced. In addition, equipment warranties may be void if specifications are not met.
There are real costs associated with health-related issues caused by dry air, including a higher occurrence of infections and increased rates of staff absenteeism. Dry indoor air can cause discomfort in the form of dry skin, eyes, and throat for staff and visitors. Humidified spaces feel warmer and are more comfortable for employees, which in turn increases their productivity with improved concentration and less fatigue.
With over 500,000 workers employed in laboratories in the United States² alone, relative humidity not only creates a more comfortable environment for workers but also reduces the spread of airborne viruses such as COVID-19 (SARS-CoV-2) and the seasonal flu, helping to protect the well-being of staff. Maintain the recommended relative humidity (RH) level between 40 – 60 % RH to lessen the impact of contagious respiratory illnesses and reduce staff absenteeism.
Due to the increase in generic drugs, manufacturers of pharmaceutical drugs have had to streamline processes and shorten the testing phase to stay competitive. Compliance to FDA or other certification bodies is a requirement for licensing, which includes documented and maintained environmental conditions including humidity levels.
As the competitive landscape changes, manufacturers of pharmaceutical drugs are looking for ways to increase productivity and eliminate waste to meet the demands of consumers. Through a customized solution specific to a manufacturer’s needs, better control of relative humidity can create an additional layer of protection to lower the risk of contamination, protect product integrity, decrease the cost of production, and minimize waste.
Types Of Humidification Systems
There are two main types of humidification technologies used to add moisture to the air of a building – isothermal and adiabatic. Isothermal (steam) humidifiers work by boiling water inside the humidifier tank and distributing it into the ductwork through a steam manifold in a duct or air-handler or directly into the space. These units use electricity, gas, or an external heat source like a boiler to change water to steam. Cleanrooms and laboratories generally use isothermal humidifiers since they produce clean and sterile steam.
Adiabatic (evaporative) humidifiers use the heat in the air to evaporate water into the ductwork or directly into the space. Adiabatic humidifiers provide humidification and evaporative cooling at the same time which provide benefits for applications with processes that create heat as in data centers, print shops, manufacturing floors, and paint booths.
Maintain the recommended relative humidity (RH) level between 40 – 60 % RH to lessen the impact of contagious respiratory illnesses and reduce staff absenteeism.
Energy And Sustainability
There are numerous energy and sustainability considerations when designing a humidification system for any facility. Depending on the application, humidifiers can consume a lot of energy. Since gas is generally less expensive than electricity, costs can be reduced by selecting a high efficiency condensing gas-fired humidifier.
Incorrectly designed dispersion systems can impact the building airflow and require the addition of fans. To combat this issue, use a maximum efficiency dispersion system with guaranteed short absorption distance for a reduced footprint and significant energy savings.
Existing isothermal humidification systems may be improved by retrofitting them with high efficiency dispersion systems, especially ones with insulated steam dispersion tubes. Utilizing a reverse osmosis (RO) or deionized (DI) water treatment system for supply water to isothermal systems will significantly reduce humidification equipment maintenance, reduce the amount of water to drain, ensure the optimal performance and energy efficiency.
Humidification technology can be installed either as a retrofit for existing buildings or for new construction. The type of indoor space, air quality goals, energy source, desired maintenance, capacity, etc. will determine the best technology for each building. Of course, energy management and the analysis of energy usage drive the selection of humidification efficiencies and sustainability.
If a building currently does not have a humidification system, it is time to add one to protect processes, equipment, health, and safety. If a humidification system exists, it should be reviewed to ensure it is properly sized, operating correctly, and energy efficient since building usage often changes over time.
Duncan Curd is Global Business Development Leader at DriSteem, provider of humidification, evaporative cooling, and water treatment solutions for commercial and industrial applications. A graduate of the University of Toronto, Duncan’s career has been focused around industrial and process automation as well as HVAC solutions. He has held a variety of management roles with Siemens including multiple business unit responsibilities. He has been active in the field of humidification as General Manager for Nortec (Condair), has held a range of advisory roles to technical colleges and universities, and is active with AHRI’s Educational committee and ASHRAE’s TC5.11 (humidification), TC9.06 and TC170 (health care facilities) committees. In addition to military service, he has been a proud volunteer with his local volunteer fire department..