Glove Box Standard Operating Procedure
Working safely within an inert atmosphere glove box requires care and co-operation from everyone who uses it. For this reason, we recommend outlining a standard operating procedure for your laboratory. Everyone with access to the glove box should agree to follow this procedure.
Standard operating procedures compliment glove box cleaning procedures, which you should perform on a regular basis as part of your maintenance routine. A good operating procedure outlines both how to enter the glove box and how to work within the glove box. It is also important to know how to use the antechamber and how to purge the glove box.
When working in a glove box, always remember the golden rules.
Glove Box Golden Rules
- Watch the oxygen and humidity levels within the main chamber. Logging the O2 and H2O levels will help you identify if there are any problems and could save your experiment.
- Always check the antechamber O2 and H2O levels before opening to the main chamber. This will help you avoid exposing the inert environment to the atmosphere outside the glove box.
- Optimize your workspace to avoid accidents. Benchtop glove boxes have limited space, so it is important to keep the glove box floor as clean as possible. Remove waste after each use and perform a quick purge if you have been working with solvents.
Entering a Glove Box
It is important to limit the exposure of the internal chamber to aqueous solutions or materials which may contain moisture (cleanroom tissue or hygroscopic materials that have been exposed to air). There are specific measures which you should take if you want to bring these types of materials into your glove box:
- Thoroughly degas porous or hydroscopic materials (cleanroom tissue, paper, cloth, etc) before bringing them in to the main glove box chamber. Normal antechamber purging may not be enough to thoroughly remove moisture. Degas any cleanroom tissue, paper or cloth under vacuum for several hours before bringing it into the glove box.
- If a solvent or material was sealed under inert conditions and has not been opened in air since, you can bring it into the glove box via the antechamber purging procedure.
- Degas hygroscopic or absorbent powders that have been exposed to air before bringing them into the glove box. We recommend that you do this for a significant period of time (ideally overnight) in a vacuum oven, or under vacuum/drying conditions.
- For all other small vials of materials and solutions that have been exposed to air, you can cycle as normal.
- Ensure all glassware and equipment is dry before entering the glove box.
We have created the following flow chart to help you decide on the appropriate steps to take before taking things into the glove box.
Additionally, it is vital to always make sure the O2 and H2O levels within the antechamber are sufficiently low before bringing anything into the glove box.
It is a good idea to always cycle the antechamber before opening the door into the main glove box, even if the O2 and H2O readings are low. This creates a good habit, which can help you avoid accidentally exposing the glove box to air in the future.
Working Within a Glove Box
The following are generally good practices for working in any glove box environment.
- Push hands into the glove box slowly. Quickly forcing your hands into the glove box will cause the chamber pressure to change rapidly. This can cause bottles or samples to fall over, and puts extra strain on the glove box gloves.
- Wear appropriate PPE while working in the glove box. If you are working with harmful substances, you may risk exposure if there is a tear in the gloves. Additionally, constant contact with skin may reduce the gloves lifetime. For these reasons, we suggest that you wear a lab coat and nitrile gloves whenever using a glove box.
- If you are using organic solvents, you must regularly purge the glove box. Solvent vapours will quickly build up in a glove box if solutions are left open. Prolonged exposure to these vapours could damage the sensor board, the O-ring seals, and the gloves. Additionally, harmful solvent vapours from the main chamber could be released into the room when you take things out through the antechamber. Wherever possible, limit chamber exposure to organic solvents (e.g. close solution bottles whenever possible), and regularly purge the glove box if solutions are open for a significant period.
- Remove all jewellery and watches before entering the glove box, as these may tear the gloves. Be careful to avoid puncturing the glove box gloves.
- Constantly monitor moisture and O2 levels during usage. Any major fluctuations in these levels or compromises in the inert environment should be logged and counteracted as soon as possible.
- If you suspect a leak at any place in the glove box, check! Use leak spray (or soapy water) to detect the presence of leaks.
- Reduced oxygen concentration within a confined space can lead to severe health effects. Check with the appropriate body for guidelines on working with asphyxiating gases. Oxygen depletion alarms can be installed in rooms where there is a pressurized nitrogen source to alert users if the oxygen concentration in the room begins to drop.
How to Use a Glove Box Antechamber
In relation to laboratory glove boxes, antechambers are small, isolated compartments. Through these, you can move small items in and out of the main chamber. This smaller vessel can be exposed to atmosphere more often than the main chamber as it will take much less time to achieve inert conditions.
In large glove boxes, the antechamber is most likely connected to a vacuum pump. After being exposed to ambient conditions, the air is evacuated out and refilled with nitrogen. After this is "cycled" several times, the antechamber can be opened to main glove box chamber.
Our glove box system features an automated purge cycle. Once started, this cycle circulates nitrogen through the antechamber until oxygen and moisture levels are consistently below set values. This is the same procedure that is used for the main chamber and should reduce the chances of accidentally exposing ambient oxygen or humidity.
Always check oxygen and humidity levels before exposing the antechamber to the main glove box.
To take samples into the Ossila Glove Box:
- First, ensure that the door between the main chamber and the antechamber is closed.
- Open the door between the antechamber and outside. Then, place your materials or equipment into the antechamber and shut the door.
- Go to the antechamber splash page and set desired O2 and H2O levels.
- Check both doors are shut, then press the "Start Purge" button on the control panel.
- Once the purge is complete, you can safely move your items into the main chamber of the glove box.
Taking samples out of the glove box requires a similar process.
- Check the O2 and H2O levels within the antechamber as per the golden rules.
- If these are higher than the desired levels, or at least not matching those in the main glove box, set the antechamber O2 and H2O levels and press "Start Purge".
- Once the antechamber purge cycle has finished, place the items from the glove box main chamber into the antechamber and close the internal door. You can then take the items straight out into ambient conditions. However, if you have been processing with hazardous solvents, it is often a good idea to purge for a few seconds before opening the glove box.
- It is good practice to cycle the antechamber at least once directly after it has been exposed to air. This reduces the chances of accidentally flooding the glove box with oxygen.
Purging the Glove Box
All glove boxes should have systems in place to maintain a constant inert environment. The Ossila Glove Box has an automated purging system where action is taken if the O2 and H2O levels drop below their set values.
If the oxygen or moisture levels increase significantly within the glove box main chamber, then the automated purging system will begin.
First, nitrogen is pushed into the system for a few seconds until an overpressure is reached. Then, some of the internal gas from the main chamber is extracted through the outlet for a few seconds.
This process repeats until enough nitrogen has been cycled through the chamber, and the oxygen and moisture levels are sufficiently low.
There are times where additional intervention is needed. For example, when working with organic solvents, vapours can quickly build up within the main chamber. This can damage the filters, gloves or sensors in the glove box, and can affect your experiment. In these situations, we recommend you perform a nitrogen "Quick Purge".
To do a quick purge, select the circulation ("Circ") icon on the main glove box page. You will get an option to set a time and number of cycles. Once these are set, simply highlight the "Circ" and press "Start Purge".
When quick purging, the system will drive nitrogen into the chamber for a few seconds, then extract internal gas out of the chamber. This is the same process that is used in the automated purge. There will then be a short 30 second rest period with no extraction or purging. This allows the system to acclimate as the O2 and H2O levels to adjust. This process repeats for the time set (e.g. for 300 seconds), and then will repeat for the number of durations chosen.
Positive vs Negative Pressure Glove Boxes.
Inert atmosphere glove boxes should be maintained at a slight positive pressure. This ensures that if there is a leak in the glove box, the internal environment will be forced out, rather than air and moisture being sucked in. We recommend maintaining the Ossila Glove Box at 1-2 mBar over ambient pressure whenever you are using it.
Leak tests however should be performed at a higher mBar. This is because when you are performing a leak test, you are trying to highlight any potential leaks. This is also true when trying to identify the source of a leak. For leak investigation, we recommend a pressure of 3-5 mBar.
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- Mary O'Kane