Fume hoods and biosafety cabinets are the two most common laboratory enclosures. Both have a partially opened side with a sliding glass sash. These enclosures function by pulling room air in through the opening, which protects the user from being exposed to the sample or substance inside the enclosure.
It’s the partially opened sash that makes a laboratory glove box a completely different enclosure. Lab glove boxes offer different options in environmental controls. Controlled-atmosphere glove boxes provide absolute control of the gas atmospheres inside the box. HEPA-/ULPA-filtered glove boxes provide absolute separation of the inside of the box from the outside laboratory environment. Procedures involving high exposure risks to deadly particulates or explosive chemicals must use a totally sealed glove box (no sashes allowed).
Choosing a laboratory glove box seems simple at first glance; the name of the glove box describes the different application and function. But within these two categories, there are many subcategories, with many features that can cause confusion. While secondary features and specifications are important to help achieve operation goals, don’t forget the first two decision points: gas or particulate control.
There are three classical states of matter: gas, liquid and solid (for this article, plasma has been intentionally excluded). So what does this have to do with the first two choices in glove box design, (controlled-atmosphere and HEPA/ULPA filtered)?
Controlled-Atmosphere Lab Glove Box
Controlling gases requires a controlled-atmosphere lab glove box designed to control the internal gas atmosphere. These lab glove boxes have valves and pressure gauges that are used to create custom gas environments. These products enable the operator to remove most of the ambient gas mixture from inside the main chamber and replace it with an inert gas. This is accomplished using a pressurized gas and a vacuum pump to push gas into the glove box and pull gases out of the glove box. Essentially, a controlled-atmosphere glove box is operated by inducing positive and negative pressure changes within a leaktight chamber. Nitrogen and argon are common inert, or noble, gases, meaning they do not react with most other chemicals. These glove boxes do not normally include filters for particulates. There can be many more functional features added to a controlled-atmosphere glove box, but without valves and pressure gauges, you can’t have control over a gas atmosphere.
HEPA/ULPA Lab Glove Box
Particulate control requires a glove box with filters; generally HEPA or ULPA filters are used to capture particulates. These glove boxes contain particulates inside the chamber, or isolate items inside from particulates on the outside in the normal air. Particulates are fine powders like soot, smoke and bacteria. Even very small liquid droplets, called aerosols, can be captured by particulate filters. Since gases are not particulates, they move freely through any particulate filter. Therefore, filtered laboratory glove boxes cannot maintain a pure gas atmosphere. There are many particulates that can be extremely dangerous to work with and must be absolutely contained within the filtered glove box to keep the operator and the laboratory safe. Alternatively, particulates can contaminate very clean or sterile samples kept inside a glove box. So filtered glove boxes can be designed to isolate sterile objects or samples inside from outside particulates. Nano-particulate research is another common application that requires researchers to use a filtered glove box. The health exposure effects to these substances have yet to be determined and human exposure is a very big concern. Yet the researchers often want to get their samples as clean as possible from outside contamination sources. So the protection is required for the sample and the person.
Once the basic application is chosen, other features can then be added to customize the box for a specific need and/or situation. Consult the manufacturer for these options.