glove box

A glove box is a device for working with chemical, biological, or radioactive materials. Typically, these materials are hazardous, toxic or both, although there are other reasons for choosing operation in a glove box. Following are some typical applications for glove boxes:

• In Biochemistry, a glove box is typically used for working with cell cultures and viruses that may be harmful to human health. Also, the glove box allows for a controlled environment (humidity, air pressure, temperature). Pharmaceuticals may have (yet) unknown effects on health, or may be toxic in high doses. These drugs are often handled in a glove box.
• Radioactive materials are also often handled in a glove box, because they can cause harm upon direct contact, or fine radioactive dust could contaminate the air and work area. Glove boxes for radioactive applications typically require extra shielding (lead glass, special gloves).
• Chemicals are sometimes too toxic, even in low concentrations to safely work with them in a fume hood. Chemicals can also react with oxygen or water vapor from the air, and decompose. In some cases, this reaction poses a hazard as well (pyrophoric materials that spontaneously combust in air). Materials can also be hygroscopic; by adsorbing water, they could become useless for a desired application. The glove box is a suitable environment for working with these materials.
• In the semiconductor industries, a clean, dust-free environment is crucial to avoid damage of the silicon wafers. For some applications, a full scale clean room isn't practical, or too expensive to operate, and a glove box may be used.

A typical setup of a glove box can be seen in the following figure. Note that this figure represents a glove box for chemical applications. Other applications may require slightly different setups.

                                              Vacuum     Inert
                                              line       flush

       Inert                                    || Valve 1 ||
       purge                                    ||___._____||
                                                |___/ ______|
        ||                                          ||
        ||__________________________________        ||
        |____                              |    _   ## Valve 2
            |                              |   |P|  ||
            |                              |____|___||_______
            |                              #  Vestibule     #
            |          Gloves       Door 2 #                # Door 1
            |         _      _             #    Tray        #
            |        / \    / \            # |____________| #
            |        \_/|   \_/|           #_|__|___|__|__|_#
            |        \  |_  \  |_          |
            |         \___E  \___E         |___
            |_________________________________ |
                                              ||
                                              ||

                                             Inert
                                             inlet
                                              

The glove box is a sealed rectangular case with a transparent (glass or plastic) front window. The side and back walls may be transparent as well. The glass has at least two glove ports, with thick rubber gloves attached (Viton or some other specialty rubber, depending on the application).

Usually, the glove box has an inlet and purge for gases. For chemical applications this is usually an inert. The choice of the purge gas depends on the application and price; helium is more expensive than nitrogen. The purge stream requires proper handling; it may be sent directly into a fume hood, or through a gas scrubber.

The vestibule is an isolation chamber for inserting and removing materials to and from the glove box. Its design is such that the environment inside the glove box is not affected by a transfer.

Materials can be transferred into the glove box as follows:

1. Make sure door 2 is closed; this door should always be closed immediately after a transfer. Make sure valve 2 is closed
2. Open door 1, and insert material to be transferred. This material must be dry, and compatible with the environment inside the glove box. Close door 1
3. Switch valve 1 to its vacuum position. Open valve 2, and evacuate the vestibule. Monitor the pressure gauge. Close valve 2
4. Switch valve 1 to its flush position. Open valve 2 and flush the vestibule with inert gas. Monitor the pressure gauge. Close valve 2.
5. Repeat steps 3-4 one or several times. For most applications, a total of three flushes is sufficient.
6. Using the gloves, open door 2 and transfer materials in or out of the glove box. Close door 2