Personal protection equipment: nitrile gloves (Part 1: A Guide to Glove Standards)
Release: 20th April 2020
Here is the base of a box of Bodyguard Blue Nitrile gloves.* Summon up your inner Robert Langdon and take a closer look!
Figure 1: The back of the box
Most are obvious or common (In the office we could correctly guess A, B, E, G, H, I, J, K). Some like C, D, F you have an idea but L was a bit of a mystery.
Here’s a quick over view (in case you have nearly finished your coffee). A longer explanation of the more obscure symbols follows later. (Fig. 1)
A= Single Use only
B= More information is provided on the leaflet accompanying the package
C= The gloves provide protection from micro-organisms (In this case bacteria, fungi and viruses)
D= The gloves provide protection against chemicals specifically Sodium Hydroxide 40% (for a minimum of 8 hours – this info is on a different table on the box - see later)
E= The material used in the product is considered safe for food contact
F= Compliant with the European Standard: approved for transient use acting as a mechanical barrier and may be sold and used anywhere within the European Economic Area (EEA).
G= keep package away from wet/damp conditions BOX
H= protect package from sunlight
I= material eligible for recycling BOX
J= product is latex free
K= product does not contain powder
L= This is The Acceptable Quality Level indicating there are less than 1.5% of the products with defects in the batch of gloves (1.5 is the European standard for medical examination gloves)
The longer read
C, D and L
The shields give an indication of what the gloves protect against. The criteria and testing methods are laid out in EN ISO 374-x;2016. This has several different sections (x) which look at the performance of the glove, covering penetration, permeation and degradation. All three factors are important when choosing a glove.
To be considered an effective barrier against either chemical or biological agents (i.e. to earn the shield) the gloves have to achieve at least level 2 in the penetration test.
Penetration is defined as the movement through pinholes or other imperfections in the glove material at a non-molecular level. Counter-intuitively it has nothing to do with the mechanical resistance of the material.
Two tests are included EN 374-2 both to assess the resistance of the glove to penetration (or freedom from holes). See Fig 2
1. Firstly the air leak test which involves inflating a glove with air pressure and then submerging it in a tank of water. Any leaks are identified by visible bubbles.
2. The second test involves suspending a glove filled with water and examining its outer surface for water droplets. The air test is not suitable for non-homogeneous gloves.
Figure 2: Air leak test
The penetration test in turn generates the AQL (Acceptable Quality Level):
Typically used for
High risk microbiology & surgery
Medical Examination gloves
Food preparation, automotive industry
An AQL result of 1.5 is the statistical probability that less than 1.5% of the products with defects, in the batch of gloves. An AQL of 0.65 assumes a more stringent quality acceptance level, allowing the wearer to have a higher degree of personal protection. (for more information about the concept & development of AQL: https://www.globus.co.uk/what-does-aql-mean)
So far so good, the batch of gloves is good enough quality to be considered chemically protective and can move on to the permeation test.
Permeation is the process by which a chemical moves through a material at the molecular level. Sometimes, permeation occurs without any physical changes to the material (such as cracking or a reduction in its elasticity), so the material can seem unaffected, even though it does not provide adequate protection for your skin.
Figure 3: Permeation test
This information is also on the glove box (for specific reagents) – see Fig. 4
Figure 4: Breakthrough
This permeation test is carried out with 18 common chemicals (see table 2) as laid down in EN 374-1.
Remember the shield with the flask & wavy lines? You have to achieve a level 1 performance (you lasted more than 10 minutes) against 1 of the chemicals on the list. These are type C gloves (Table 3).
The code letters of the chemicals the results were achieved with, are displayed under the shield (Fig. 1 D).
For anyone working extensively with a particular solvent it is well worth checking your gloves are the correct type.
But wait, there’s more to consider. Not only do you need to know that your gloves can stop the chemicals getting to your skin, you need to know what actually happens to the glove material on prolonged contact with the chemical. This is measured by ENS374-2-4 and is called degradation.
Degradation is a deleterious change in one or more properties of a material due to contact with a chemical, such as flaking, swelling, disintegration, embrittlement, discolouration, hardening or softening.
Degradation testing is designed to check how a glove performs in the real world. In the other tests sections of glove material are clamped flat, but most users are flexing their gloves. If the glove becomes brittle it may crack when you grasp something. It doesn’t matter that the materials can withstand 8 hours in peroxide if when you actually use them they develop cracks and tears which allow the chemicals onto your skin.
The test consists of measuring the force required to puncture the glove before and after exposing the glove material to the test chemical for 60 minutes. The test result is reported as a percentage degradation, so values could be positive (if the material has become weaker after chemical exposure) or negative (if the material has become harder after chemical exposure). This information should be given alongside the code letter of the chemical tested. (See Fig. 4.)
In order to earn the protection against micro-organisms shield, the gloves need to pass the penetration test (outlined above). They are then considered to be effective against fungi and bacteria.
In order to be considered as an effective barrier against the much smaller virus (Figure 6), they must pass a penetration test with a broth containing the Phi-X174 bacteriophage as covered in EN 374-5
There are lots of other bits of legislation covering design, sizing, dexterity and materials used in glove construction, which have to be passed before the gloves get through to the testing outlined here.
Figure 5: Microorganism size
So what have we learned?
If you work with a particular solvent a lot: check your glove provides a barrier. Remember you might not be able to see or feel a change.
With protective gloves, both the material the glove is made from and its thickness are important factors. A disposable natural latex glove will, for instance, often give barrier protection against only dilute aqueous chemicals. However, a thicker Neoprene or PVC gauntlet would be expected to give acceptable resistance against organic solvents such as methanol and acetone.
Do not use the gloves for longer than recommended by the index. Only use disposable gloves for one session. Adding up the number of minutes over various moments or days is not valid because the gloves are affected by the liquid chemicals after first contact.
The lower the AQL number rating, the greater the quality of barrier protection the wearer will have.
If in doubt call us!
*The product used is our catalogue number 410-AL-303 which are disposable nitrile gloves from Polycohealthline ref.: GL8903.
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