In my understanding it makes much more sense to run the glovebox in overpressure conditions, as in case of a leakage only inert gas will flow out, but no oxygen and water will find the way inside. In the opposite case, with underpressure, a leakage would cause the oxygen- and water-containing atmosphere to get sucked into the box which could cause severe problems. If enough O2 and H2O get into the glovebox the electrolytes will be contaminated and alkali metals might catch fire. That should convince your health & safety department, I bet they do not want your glovebox to burn.

In my understanding it makes much more sense to run the glovebox in overpressure conditions, as in case of a leakage only inert gas will flow out, but no oxygen and water will find the way inside. In the opposite case, with underpressure, a leakage would cause the oxygen- and water-containing atmosphere to get sucked into the box which could cause severe problems. If enough O2 and H2O get into the glovebox the electrolytes will be contaminated and alkali metals might catch fire. That should convince your health & safety department, I bet they do not want your glovebox to burn.

As mentioned by Sebastian safety issues in working with glove boxes is definitely with slight over pressure.

Being also responsible for chemical lab safety I guess it might be a misunderstanding of your Health & Safety department because chemical labs where our glove boxes are being used, of course run in under pressure environment avoiding gases etc. reach the offices and floors.

Never saw a working glove box with the gloves pulled in! Must over pressure to cover leaks and maintain purity when opening the locks.

the simple answer is underpressure will drive moisture and air into the box when using the locks no matter how many purge cycles. At best you will have poor battery performance, at worst a fire.

Many thanks for the answers and help!

Many thanks indeed to all involved. Let me however now raise the complexity of the problem. Vanessa did not mention in her problem setting the fact that some of the materials dealt with in the glove box is labelled as toxic. The manual of the glove box clearly states that under these circumstances the glove box must operate in under-pressure mode. It is exactly the same case as for all glove boxes dealing with radioactive substances all over the world. You want to minimise the probability that dangerous materials leave the glove box.

This causes obviously a dilemma: scientists need to work on over-pressure, to avoid battery/cell contamination by moisture and oxygen, technicians would like to ensure minimisation of the probability to contaminate the lab environment.

I suspect that the dilemma can be at least simplified by performing a quantitative risk assessment.

Was some of those participating to this tread confronted with the dilemma? Which is the solution?

Is a risk assessment available in your labs, which we could use?

First of all, dear Dr. P. Moretto, could you more precisely indicate which hazardous substances are in the glove box used by electrochemists? Generally, if there are any, these should be in closed containers, even if these are inside the box. I'm not saying that box should be clean always... In addition, the boxes are usually equipped with a dust filter as well as a solvent filter.

So, will return to the question.

In laboratory practice, I have never seen (and have never worked this way myself) somebody who works in a glove box under reduced pressure. Usually, an unused glove box is at a slightly increased pressure (I always set the pressure change limits from -0.003 (5) to 0.006 (8) bar, but each (reasonable) colleague who passes past the box usually makes the pressure slightly positive (0.002 approximately) so that the gloves protrude outside). As our colleagues rightly point out, this protects the atmosphere of the box from outside leakage. At the beginning of work, any experienced user slightly lowers the pressure in the box to be able to put his hands in gloves. After the hands are inserted into the gloves, the pressure slightly increases (by the pedal ...), to about 0-0.001, otherwise it is impossible to work. Moreover, the operator sometimes slightly changes the pressure during the work (depending on the operation he performs). Sometimes box is busy almost all working hours, will these guys order to keep there low pressure all the time? It is necessary to catch one the most active and enforce him work in box under reduced pressure for at least half an hour (if you not pity of box). Or let them pay for spoiled lithium, additional regeneration gas, etc.

But in no case tell them that a whole argon cylinder (I don’t know how long time you use it) sooner or later pass into the atmosphere of a working room ... Gas (in absence of Safety guys) has no other way ...

If we look at the problem from a more official side, safety in the laboratory is not governed by the views of representatives of H&S service, but by quite specific state rules for working with hazardous substances. If there is a suspicion that one of these substances is present in the atmosphere of the laboratory, then it is necessary to analyze air samples and check whether their concentration exceeds the TLV, or is within the permissible norm (ADI). If the presence of a concentration of a hazardous substance exceeding the TLV is detected instrumentally, then actions should be taken to identify the source of contamination, as well as stop it. But, based on my experience, I can say that the glove box is not the worst source of pollution in the chemical laboratory.

I remember very well how we eliminated mercury pollution in one of the rooms. It took almost a year (for example, it was necessary to remove and dispose of all coatings from the walls and the floor) and only after 5 or 6 analyzes the room was recognized as a working. And the problem was simple: one moron worked with mercury compounds and accidentally dropped the test tube with these on the floor ...