click to enlarge
Triplex central vacuum system pumps support suction applications at Yale Univ. Amistad Bldg. Image: Vacuubrand   

Are you designing vacuum into labs, or designing labs in a vacuum? While vacuum is a utility that is commonly required for labs, along with electricity, water and compressed air, many architects, engineering consultants and lab planners are unfamiliar with the scientific uses of vacuum in labs or the different levels of vacuum needed for those tasks. Without such an understanding, how can you be sure that you will deliver a lab with a key utility that supports the intended scientific program?

Let’s take a brief look at scientific vacuum—specifically, the nature of lab vacuum operations, how the vacuum needs of scientists vary by discipline and the implications of the users’ different needs for this important utility in science building design.

The Major Uses of Vacuum
Lab vacuum is commonly used for one of four classes of operations:

  • Suction.
  • Evaporation.
  • Fine-vacuum applications.
  • Instrumention/detection/

Suction applications require very modest levels of vacuum—just enough to create a pressure difference that causes a liquid to move. Typical operations include filtration—using the pressure differential created by the vacuum to make the process proceed more quickly—and liquid aspiration, in which vacuum is used to suck liquid up a tube, typically for transfer from one container to another. Suction applications are well within the range of a central vacuum system, and are also supported with small diaphragm pumps or local vacuum networks. Excess vacuum in these applications—say, from a rotary vane pump—can cause inadvertent evaporation of the liquids.

In evaporation applications, vacuum is used to lower the boiling point of a liquid. For example, water and other solvents can be induced to boil at room temperature. This principle can be helpful if the material will degrade at higher temperatures, or to separate a mixture of solvents or concentrate a residual material. Evaporative vacuum is used in such devices as rotary evaporators, vacuum ovens, gel dryers and centrifugal concentrators. Reaching evaporative levels of vacuum requires either dedicated pumps on the bench, water jet aspirators or local vacuum networks supported by oil-free pumps capable of these vacuum levels.

Fine vacuum” describes applications that need much deeper vacuum—pressures 1/1,000th of those used for most evaporative work, and 1/100,000th of that provided by central vacuum. Such fine-vacuum supply is needed to operate Schlenk lines and for molecular distillation applications, as well as for freeze dryers. Fine-vacuum levels cannot be reached with central vacuum and require dedicated pumps using rotary vane or scroll technologies. The lab designer or architect must mainly make provision with noise-reducing vacuum pump cabinets and exhaust points.

Vacuum used for detection or instrumentation is often referred to as high vacuum or ultrahigh vacuum, and is typically intended to remove 99.999999999%  or more of the remaining air and the associated impurities in a sample chamber. These vacuum levels create conditions for demanding physics operations, or allow sensitive instruments like mass spectrometers to analyze a virtually pure sample. Vacuum needed for these applications require specialized pumps—such as turbomolecular pumps—that are usually contained in the instruments.

Who needs what vacuum?
Since scientists of different disciplines make different use of vacuum, they need different vacuum levels in their labs. To ensure that the lab you design meets the needs of the scientists who will be using it, it is always best to discuss with the scientists the specific vacuum applications they will employ. Yet, there are some common operations typical of the various scientific disciplines that give you a starting point for such programming discussions.


click to enlarge
Local vacuum network pump supports several fume hoods at the new Johns Hopkins Univ. Mudd/Levi Hall undergraduate chemistry labs. Image: Vacuubrand   

Chemistry labs (including the several sub-disciplines) tend to have complex vacuum requirements. Suction-level vacuum is used for filtration and sample prep operations. Evaporative applications are common and need deeper vacuum than central vacuum can supply. They also benefit from electronic vacuum controls that optimize process conditions and protect samples. Chemistry research labs usually also need pumps that can achieve fine-vacuum levels for Schlenk lines and molecular distillations. Given this range of requirements, it is common for chemistry labs to need vacuum supply from bench turrets or local vacuum networks, evaporative vacuum from dedicated pumps or local networks and dedicated fine-vacuum pumps.

Biological disciplines use mainly suction-quality vacuum, such as the aspiration operations used in cell culture and tissue culture. Evaporative vacuum may be needed to accelerate the drying of genetic materials on electrophoresis gels, so dedicated pumps or local vacuum networks capable of evaporative-vacuum levels may be needed. Biological labs sometimes also use freeze dryers, which need pumps (rotary vane or scroll) capable of fine-vacuum levels to force a frozen sample or its solvent to “sublimate”—go directly from solid to vapor.

Physics/materials/instrumentation labs rarely need either suction or evaporative vacuum; vacuum is typically used for evacuating air and gases from a sample chamber so that uncontaminated samples can be analyzed or modified. The ultrahigh vacuum required is usually produced by pumps in the instrumentation itself. Apart from space planning and exhaust management, vacuum supply to these labs is not usually a concern of the planner or architect.

Environmental and geological science labs use a wide range of techniques that combine vacuum operations from life sciences, chemistry and physics. Any of the vacuum apparatus used in biological, chemistry or physics labs may be needed. Discussions with intended users are the only way to ensure that the vacuum supplied in the construction process will serve the scientists’ needs.

Dry labs for computer analysis and modeling are an increasing presence in all areas of the sciences, complementing the work going on in the “wet labs.” In these labs, powerful computers analyze data and manipulate 3-D models of chemical compounds, nanomaterials, biological molecules and sub-atomic particles. Since these labs use virtual samples instead of physical samples, building vacuum is rarely needed.

Plan for Adaptable Vacuum
Given the very different vacuum conditions needed in labs, it is clear that suction-quality vacuum from a central vacuum system is likely to meet the needs of only a small subset of vacuum users. Yet, the widespread use of vacuum in science means that leaving vacuum out of your planning will force scientists to rely on individual pumps for every vacuum application, with the obvious space, energy and exhaust-management implications. A better alternative is to rely on modular vacuum technologies that serve multiple users, operate on demand and are flexible enough to adapt over time to changing scientific or budget priorities.

When designing new or renovated lab space, especially in multidisciplinary buildings, you improve the likelihood that you will satisfy your client’s science and sustainability objectives if you give careful consideration to how your plan supports the likely vacuum operations in the space.