Choosing the right chemical-resistant gloves: EN ISO 374 explained simply
A splash of cleaning agent, reaching into an alkaline solution, or prolonged contact with a solvent: chemicals can come into contact with hands in many different ways during everyday work. Protective gloves are often selected based on the material, the pictogram, or the general statement “chemical resistant.”
However, neither “nitrile” nor the chemical protection pictogram means that a glove provides sufficient protection against every hazardous substance. One glove model may withstand a particular acid for a long time, while losing its protective properties much more quickly when exposed to another substance. Concentration, temperature, and type of contact also play an important role.
EN ISO 374 helps to classify chemical protective gloves more effectively. This article explains what Types A, B, and C, the code letters, and terms such as permeation, penetration, and degradation mean – and what purchasing and occupational safety teams should consider when selecting gloves.
What Does EN ISO 374 Regulate?
The EN ISO 374 series of standards specifies requirements and test methods for protective gloves against hazardous chemicals and microorganisms.
The most important parts are:
- EN ISO 374-1: Requirements and marking for chemical risks
- EN ISO 374-2: Testing for penetration through holes or other defects
- EN ISO 374-4: Testing of material degradation caused by chemicals
- EN ISO 374-5: Requirements for protection against microorganisms
Chemical protective gloves generally fall under PPE Category III. Our article on PPE Categories I, II, and III explains what this classification means for testing and marking.
Note on the current status of the standards: The international standards ISO 374-1 and ISO 374-5 were revised in 2024. In the current Official Journal of the European Union, the references EN ISO 374-1:2016 and EN ISO 374-5:2016 are still published as harmonized standards.
What Do Types A, B, and C Mean?
Chemical protective gloves are classified into Types A, B, and C according to their permeation performance.
| Type | Minimum requirement |
|---|---|
| Type A | At least performance level 2 against at least six test chemicals |
| Type B | At least performance level 2 against at least three test chemicals |
| Type C | At least performance level 1 against at least one test chemical |
Performance level 1 corresponds to a standardized breakthrough time of at least ten minutes, while performance level 2 corresponds to at least 30 minutes.
More code letters do not automatically mean greater protection for a specific application. What matters is whether the glove provides sufficient resistance against the substance actually being used.
A Type A glove has been tested against more reference chemicals than a Type B or Type C glove. However, this does not establish a general ranking for all applications. A Type B glove may be better suited to a particular hazardous substance than a Type A glove that does not provide sufficient resistance to that substance.
What Do the Letters Under the Pictogram Mean?
Under the chemical protection pictogram, gloves of Types A and B display code letters. Each letter identifies a specific test chemical against which the glove has achieved the required permeation performance.
The following reference chemicals are relevant for ASATEX models 3450 and 3490:
| Code letter | Test chemical |
|---|---|
| A | Methanol |
| J | n-Heptane |
| K | Sodium hydroxide, 40% |
| L | Sulfuric acid, 96% |
| M | Nitric acid, 65% |
| O | Ammonia solution, 25% |
| P | Hydrogen peroxide, 30% |
| T | Formaldehyde, 37% |
EN ISO 374-1 includes a total of 18 specified test chemicals. The code letters indicate which of these reference substances the required performance level has been achieved against. They do not indicate general resistance to all acids, alkalis, solvents, or mixtures.
Important: The table only shows the reference chemicals relevant to the ASATEX gloves mentioned above. It does not replace a product-specific resistance chart for the substance actually being used.
Permeation, Penetration, and Degradation: What Is the Difference?
Three processes are crucial when assessing a chemical protective glove.
Permeation
Permeation refers to a chemical passing through the glove material at the molecular level. The substance can penetrate the material even though the glove still appears intact on the outside.
During testing, the time required for a specified permeation rate to be reached on the inside of the material is measured. This results in the standardized breakthrough time.
Penetration
In the case of penetration, a chemical enters the glove through holes, cracks, or other defects. Impermeability is tested, among other methods, using water and air leak tests.
Degradation
Degradation describes the harmful alteration of glove material caused by contact with chemicals. For example, the material may swell, become discolored, brittle, or lose strength.
Testing in accordance with EN ISO 374-4 examines how the puncture resistance changes after contact with a test chemical. For the chemicals used in permeation testing, degradation results must also be stated in the user information.
A glove should therefore not be selected based solely on its breakthrough time. Its impermeability and any changes to the material caused by the substance must also be taken into account.
Is the Breakthrough Time the Maximum Wearing Time?
No. The standardized breakthrough time is a laboratory comparison value and does not represent a binding maximum wearing time for the workplace.
The actual protection time can be influenced by factors including:
- Temperature
- Concentration and composition of the substance
- Splash contact or complete immersion
- Mechanical stress and stretching
- Condition and previous use of the glove
Studies by the Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA) show that chemical protective gloves can reach significantly shorter breakthrough times under real working conditions than under the specified test conditions. Companies should therefore establish an application-specific replacement schedule and clear rules for disposal.
What Does the “VIRUS” Marking Mean?
The microorganism pictogram without an additional marking indicates protection against bacteria and fungi. If the word VIRUS appears underneath, the glove has additionally undergone a virus penetration test in accordance with ISO 16604. The bacteriophage Phi-X174 is used as the test virus.
Virus protection is an additional property. It does not replace the assessment of chemical resistance and does not indicate which hazardous substances the glove can be used with.
How Can You Select the Right Chemical Protective Glove?
The selection should not be based solely on the material, pictogram, or type designation. A sensible process includes the following steps:
- Identify the hazardous substance: Clearly identify the chemical or mixture.
- Check the safety data sheet: Pay particular attention to the information on personal protective equipment.
- Assess the conditions of use: Take concentration, temperature, type of contact, and duration of contact into account.
- Compare manufacturer information: Check the resistance and test values for the specific substance.
- Consider other hazards: For example, mechanical stress, heat, or biological risks.
- Determine the fit and glove length: The glove must fit securely and allow the required level of dexterity. Gloves that are too large can impair grip security; an unsuitable size can also make handling more difficult.
- Establish replacement and disposal procedures: Replace damaged, degraded, or contaminated gloves in good time.
The safety data sheet is an important starting point. For the specific selection, the user information and the chemical resistance data provided by the glove manufacturer should also be consulted.
Two Type A Gloves with Different Designs
The ASATEX chemical protective gloves 3450 and 3490 both meet the requirements for Type A. Nevertheless, they differ in their construction and primary areas of application.
Chemical Protective Glove 3450
The 3450 is a classic nitrile chemical protective glove with a cotton flock lining. Its Type A marking includes the test chemicals J, K, L, O, P, and T. It also provides documented protection against viruses.
Chemical Protective Glove 3490
The 3490 features a polyamide-carbon liner with a full nitrile coating. It is classified as Type A with the code letters A, J, K, L, M, O, P, and T and has also been tested for protection against viruses. Its construction combines chemical protection with dexterity and secure grip. In addition, capacitive touchscreens can be operated without removing the gloves.
The suitability of a glove is not determined solely by the number of code letters. The decisive factors are the chemical being used, the working conditions, and the additional requirements of the task.
Frequently Asked Questions About Chemical Protective Gloves
Is Type A Always Better Than Type B?
No. Type A demonstrates the required permeation performance against a greater number of reference chemicals. However, when selecting a glove, the key factor is whether it is suitable for the specific substance being used.
Does a Nitrile Glove Protect Against All Chemicals?
No. Resistance and breakthrough time depend on the exact material composition, material thickness, and manufacturing process. Nitrile gloves can therefore achieve different test values when exposed to the same substance.
Is the Breakthrough Time Also the Maximum Wearing Time?
No. It is determined under specified laboratory conditions. Temperature, movement, stretching, and actual working conditions can significantly reduce the actual protection time.
Can Chemical Protective Gloves Be Used More Than Once?
Whether a chemical protective glove can be reused depends on the manufacturer's user information, the hazardous substance used, and the specific conditions of use. In cases of uncertain residual contamination, damage, or visible changes to the material, the glove must not be reused.
Conclusion: The Type Alone Is Not the Deciding Factor
EN ISO 374 provides important guidance when selecting chemical protective gloves. However, Type A, B, or C, code letters, and breakthrough times only represent part of the overall protective performance.
The decisive factors are the specific hazardous substance, its concentration, the temperature, the type of contact, and the actual working conditions. Only by comparing these factors with the manufacturer's specifications can you determine which glove is suitable for the intended task.
Need help selecting the right glove? Get in touch with us – the ASATEX team will be happy to advise you on suitable chemical protective gloves for your application.