The other day I was asked about glove selection for use in a Class III BSC and whether there were options other than butyl rubber.

             Gloves are supplied in a variety of materials from several manufacturers.  These materials include neoprene rubber, butyl rubber, and hypalon and have differing permeability rates with various chemical compounds (including decontamination chemicals). The selection of glove type should be made based on risk assessment that considers chemical permeability, operations (handling of animals or sharps), and the requirement for dexterity.  Start by consulting with a glove permeability chart when use of chemicals is anticipated, and for more specific information, contact the glove vendor for break through rates with the particular glove and chemical you plan to use.  This will help in the selection of the correct glove, as well as the time required to change the gloves before they break through. Strict specifications have been developed for butyl gloves by DOD. Consideration of the operation being performed is essential as the glove types differ significantly in the amount of dexterity needed; with butyl offering less dexterity than hypalon.

             Gloves are available in different thicknesses and hand sizes.  A balance between dexterity and protection should be considered in a risk assessment when specifying glove thickness.  Ordering the correct hand size is important for safety and ability to perform the work when using the gloves.  Gloves that are too large create a ballooning effect making it very difficult to manipulate equipment such as pipetters, small tubes, plates and other common items.  This increases the risk of a spill, contamination of the material and causes worker fatigue.

              Two part arm sleeve and glove systems are available.  This enables the user to select from a variety of gloves and sizes (to include exam gloves, nitrile and other gloves commonly used in microbiological laboratories) which greatly increases dexterity.  However the circular connector between the attachable glove and arm sleeve can be difficult to clean and thoroughly decontaminate. If this system is used, SOPs for thorough decontamination should be in place and personnel should practice decontaminating the glove and ring system (attaches the glove to the sleeve) prior to conducting work with pathogens.

hypalon glove

neoprene glove

Two-part glove system

   Gloves should be carefully inspected before commencing work within a Class III BSC.  While the entire glove and arm length should be inspected, particular attention should be given to the fingertips, the webbing between the fingers, and the connection point to the glove port.  These are areas which are most susceptible to wear, stress and operational damage.  Gloves should be visually inspected periodically for cleanliness during work, and especially if you suspect a breach may have occurred.  One advantage of hypalon gloves is that they are white in color making it easy to spot surface contamination. Gloves should be replaced when any cracks, wear areas, or tears are observed or if break through is suspected. 

             Even though work is conducted wearing gloves (typically an under glove and the outer glove attached to the Class III), personnel should thoroughly wash their hands after working in the Class III and prior to exiting the laboratory.

References:

 1. Glove selection chart

http://www.chem.duke.edu/safety/glove.html

 2. Glove permeability

http://www.himnrbehs.com/himnrbehs/pdf/2002-02-19%20Glove%20Safety%20Booklet.pdf

 3. MIL DTL 43976D (Military Standard for gloves); Dept of Defense, 2003

http://assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=24055

    There are several technologies typically used to transfer samples, materials and waste into and out of the Class III BSC. These include dunk tanks, pass through chambers, double door autoclaves and rapid transfer ports (RTP). 

    Dunk tanks allow for the passage of potentially contaminated materials out of the BSC without breaching containment.  It also allows for live samples to be removed for transfer to another lab or for archive.  The exterior of the primary container is surface decontaminated and packaged in a secondary container which is kept in contact with a chemical decontaminating solution in the dunk tank for a prescribed period of time.  The decontaminant and contact time are specified in laboratory SOPs, as is how frequently the decontaminant should be changed, and how recently it should be prepared prior to conducting work in the BSC.  The liquid must also be checked to ensure it is one inch, or the level specified by the manufacturer above the stainless steel divider that bisects the dunk tank.  Having a liquid level above the divider is needed to maintain containment and separation of unfiltered air from the room and Class III BSC.

       Dunk tanks can be designed with coved or oblong shapes for ease of cleaning, may be slightly graded for ease of draining, and can be designed with ‘cages and polls’ to keep containers and bags submerged, and retrieve the cages from the bottom of the tank for easy removal.  Kynar or Halar coatings should be bonded to the interior surfaces of the stainless steel dunk tank to protect them from the corrosive effects of many decontaminants.  A latch and administrative SOP or a timed interlock ensures both lids of the dunk tank are not opened at once, and that the material has been in appropriate contact with the decontaminant.

Oval slide-out dunk tank

    Pass through chambers allow for clean materials to be passed into the Class III BSC.  Potentially contaminated materials should not exit the BSC via the pass through chamber unless they are double contained with the package surfaces decontaminated.  The interior of the chamber should be surface decontaminated when materials are passed from the Class III to another location as even though the containers are surface decontaminated, there could be trace contaminants on the gloves, which could then contaminate the pass through chamber.  Once the inner door has been opened (between the chamber and the BSC) the chamber should be sprayed and surface decontaminated at the end of the experiment, or prior to opening the outer door that interfaces with the room (i.e. when additional supplies are to be introduced into the pass through chamber to the BSC).

       Pass through chambers doors are gasketted and airtight, and the chamber may be non-ventilated, or ventilated with the exhaust air HEPA filtered prior to release.  Typically the chambers have two doors, one that traverses the lab to the interior of the chamber and the other which connects the interior of the chamber to the interior of the BSC.  There can be doors servicing other areas as well. All doors should be interlocked, with an audible and visual alarm indicating when a door is not fully closed after an appropriate period of time has elapsed to transfer materials. 

Pass through chamber view on Class III BSC exterior

   Double door autoclaves are very useful in passing large items into the Class III BSC and to sterilize bulky waste and material at the end of the experiment.  The 5^th Edition BMBL advocates a double door autoclave be integral with the Class III BSC for BSL-4 cabinet laboratories.  

Double door autoclave integral to Class III BSC

    Rapid Transfer Ports (RTP) provide the user a safe, efficient and time saving method to introduce and remove material from a Class III BSC without potentially contaminating the laboratory.  RTP come in a variety of sizes ranging from small to very large cart mounted versions for animal transport in containment.  They can be made in stainless steel or high durability plastic. 

       The RTP maintains containment as its design features a beta flange lid exterior that mates to an alpha flange door exterior that is attached to the Class III BSC.  The lid and door are rotated and sealed and must form an interlock before door inside the BSC can be opened.  This exposes only the interior of the RTP cylinder to air and materials inside the BSC.  The process is reversed to uncouple the RTP.  The contents can be stored or the RTP can be opened with an allen key inside a Class II BSC where the materials are removed and the interior of the RTP is surface decontaminated for reuse.

Exterior of the sealed RTP being mated to the exterior of the BSC

Sands Exposition Center
Las Vegas, NV, USA
Germfree will be showing their equipment in Booth#1310
http://www.ashp.org/midyear2009