On September 19, 2021, we reminded readers that chlorine, the first combat gas used by the German army in Ypres in 1915, continues to be regularly used on battlefields and/or in acts of chemical terrorism (see NRBCe: Terrorist Chemical Weapons Attacks).
The Issue
Chlorine is widely available and in large quantities, as it is used in household and industrial applications. It easily forms a true gas due to its high vapor pressure and poses a significant risk of accidental or deliberate release, as seen in conflicts from World War I to the current Syrian conflict. Thus, chlorine remains a persistent threat to both civilian and military populations in future conflicts or acts of terrorism, in addition to the danger of accidental domestic or industrial exposure.
Where can you be exposed to chlorine?
Chlorine gas can be found in numerous fields, including industrial (chemicals, pharmaceuticals, food, water treatment), agriculture (water, soil, and seed disinfection), and as part of chemical weapon arsenals.
Civilian populations are not immune to chlorine poisoning: most civilian chlorine gas exposures reported in medical literature are associated with industrial accidents, including transportation, or the use of swimming pools. Most cases exhibit acute respiratory symptoms, mainly coughing and dyspnea, along with eye and throat irritation. The development of pulmonary edema or Acute Respiratory Distress Syndrome (ARDS) is rare, and the incidence of deaths is low (0.6%), with a good prognosis for the majority of patients.
The Gas Effect
The introduction of gas warfare during World War I had a significant impact. Gas injuries caused 91,000 of the 1.3 million deaths in World War I. Chlorine, phosgene, and mustard gas were all used during this time, causing unprecedented injuries. As gas victims increased, doctors and nurses had to treat these conditions as best as possible. Chlorine was the first of these gases to be used.
Military cohort studies from World War I reported a high incidence of acute respiratory disorders but low mortality rates, generally below 5%, and relatively few chronic respiratory symptoms. Chlorine exposure, typically released from high-pressure bottles during previous conflicts, was associated with eye irritation, upper respiratory tract irritation, central airway irritation, and pulmonary edema. Victims generally developed non-cardiogenic pulmonary edema about 12 hours after exposure, and death occurred between 24 and 48 hours post-exposure.
The invention of war gases necessitated the development of protective gear for soldiers’ bodies and respiratory tracts on the battlefield.
How to Protect Yourself
Currently, professionals like the military wear CBRN combat suits that protect against various gases. Intervention forces, such as RAID, BRI, and GIGN, are also equipped with CBRN protective suits (TFI®: Intervention Forces Suit). These protective suits are also available for professionals dealing with chemicals: the Polycombi® multipurpose CBRN protection suit, the Polyagri for farmers, and the Polyindus used in industrial settings.
All these products are based on a common principle: filtered suits, each tailored to its specific use.
Filtered vs. Sealed Suits
To protect the body against gases and other toxic substances, whether liquid, vapor, or aerosol, it might seem logical to use a completely sealed suit, preventing toxic molecules from penetrating the textile and reaching the skin. However, this is a false good idea!
Why? A sealed suit, while preventing toxins from passing from outside to inside, also blocks the passage of sweat from inside to outside, quickly turning the garment into a hot, water-saturated oven.
For the final assembly of the garment, there are two opposing concepts:
Sealed Concept
Currently, sealed suits are mainly made of polyethylene. These protective garments meet “type 3” criteria, meaning liquid-tight. The completely sealed material blocks both liquids and gases. While seemingly reassuring, this does not account for two fundamental limiting aspects: the physical and chemical properties of a suit do not consider that; – a suit consists of fabric but also seams and interfaces; – a suit is worn by an individual whose physiological constants must be respected, particularly body temperature and hydration. Comfort must also be considered (body comfort, sensory comfort, task comfort, etc.).
Filtered Concept
Characterized by its air permeability, it employs two layers of textile with a filtering lining capable of adsorbing toxins. This complex allows sweat and heat evacuation, thus better thermoregulation. We remind that sweat evaporates, drawing energy from the skin and cooling it, positively affecting body temperature regulation.
Figure 1: Schematic diagram of the textile filter complex: The activated carbon microbeads are clearly visible.
Comparison of the Two Concepts in Use
In this context, we compared these two concepts not at the elemental level but at the entire garment level under real usage conditions. The results obtained with a sealed suit were compared with those of an CBRN filtering suit (Polycombi®) under operational conditions.
Experimental Protocol
We used a dynamic method. About thirty sensors sensitive to methyl salicylate (MS = mustard gas simulant) were placed on the bodies of test subjects, either wearing a type 3 impermeable suit or a filtering suit and operating in an atmosphere containing MS. These sensors measured the penetrating doses of the product.
Methyl salicylate, at a concentration of 65 mg.m<sup>-3</sup>, was used as a mustard gas simulant. The SD liquid method was employed to measure permeation. For physiological tests under operational conditions, we used the US MIST (Man in Simulant Test) protocol.
Thirty passive dosimeters were positioned on individuals under the suit, as described in figure 2. They measured the penetrating doses of the simulant at 8 parts of the body: 1- nape, 2- back shoulders/nape, 3- front shoulders, 4- torso, 5- forearms, 6- upper legs, 7- lower legs at the front, 8- lower legs at the back. All interfaces (hoods, gloves, feet) were sealed with adhesive (tarlatan).
The subjects repeated 80 basic movements identified in operation (figure 3) for 1 hour in a chamber simulating a wind of 1 m.s-1.
Figure 2: Positioning of the 30 passive dosimeters
Figure 3: 80 elementary gestures representative of operational activity
Results
a) In Vitro Permeation Test
| Type 3 Impermeable Textile | 0 µg.cm² for 24 hour |
| Filtering Suit | 0.1 to 0.5 µg.cm² for 24 hours |
b) Physiological Tests on Worn Equipment
| Average penetration for Type 3 suit | 408 mg.min.m-3 |
| Average penetration for filtering suit | 18 mg.min.m-3 |
Figure 4. Detailed results according to body parts for the passage of the simulant.
Interpretation
The in vitro tests show that the material constituting the Type 3 suit does not allow any substance to pass through, while a small amount of liquid penetrates the filtering textile within 24 hours. These results are entirely consistent with expected outcomes.
Regarding in situ tests, the average penetrating doses of 408 mg.min.m³ are approximately 20 times greater than those of filtering suits, which are only 18 mg.min.m³. These results, completely contradicting the apparent behavior of the materials constituting the suits, can be explained by the so-called “pumping” effect.
Air intake due to the depression induced during abrupt movements is inevitable and significantly increased when the suit is airtight: indeed, air will enter at high speeds through poorly managed interfaces or other accidentally or intentionally made openings. Critical passage points are the forearms, crotch, and neck.
In the case of filtering suits, the pumping effect is reduced because air penetrates uniformly over the entire surface of the textile constituting the equipment (approximately 3 m²), the internal depression is thus lower, and the local velocity of the gas flow is reduced. Additionally, as this entire surface consists of a carbon-lined inner layer, it can re-adsorb toxic products more quickly than the skin (the differences in adsorption enthalpy of the filtering lining and the skin favor the textile).
Conclusion
Not only do CBRN filtering suits protect better than Type 3 suits, but they are also physiologically more tolerant and robust. Filtering solutions, therefore, offer the best compromise of protection/mobility/robustness, reducing personnel rotations and the number of suits needed in ramping up a rescue system. The Ouvry® filtering Polycombi® also protects against liquid chemical projections, very useful for handling incapacitated victims.
Comparison of chlorine protection between a phytosanitary protective suit and the Ouvry PolyAgri® (filtering)
Experimental Protocol
The sensors were replaced with an undergarment covering the entire body and containing a color indicator across its surface that turns from yellow to red in the presence of chlorine.
The subjects wore either an agricultural phytosanitary protective suit or the Ouvry PolyAgri® PPE suit. They moved in a chlorine-laden atmosphere at a concentration of (3.0 ± 0.2) ppm, a temperature of (20 ± 2)°C, a relative humidity of (44 ± 5) %, and a duration of (30 ± 1) minutes. The suits were complemented by gloves, boots, and protective masks with filter cartridges. They performed standardized movements representative of agricultural activities.
At the end of the exercise, a simple visual analysis of the suit initially highlighted color changes from yellow to red at the exact locations where the test gas, chlorine, penetrated. Then the undergarments were analyzed using a colorimetric device called LUCY.
For better visualization of color changes and quantitative analysis, the colored spots are converted into pseudo-colors representing different concentrations, with color intensity determined from a calibration curve. The device calculates an “Adjustment Factor (F)” which is the ratio of the theoretical amount of gas applied outside the suit to the amount of gas that penetrated. The higher F is, the better the protection.
A “Protection Factor (Kp)” is derived, which is the percentage of chlorine that penetrated relative to the total amount of chlorine applied to the garment. The smaller Kp is, the better the protection.
Kp = 100/F (%)
Figure 5: Results for the agricultural suit
Left: standard protective suit, center: undergarment measuring chlorine, right: quantitative colorimetric analysis (scale in µg/cm²).
Figure 6: Results for the PolyAgri
Left: filtering PolyAgri®, center: undergarment measuring chlorine, right: quantitative colorimetric analysis.
Results
It is already easy to see with the naked eye that the yellow undergarment has many red spots in the case of the standard suit. Therefore, a large amount of chlorine has passed under the protective clothing, which is confirmed by the colorimetric analysis showing many spots. In the case of the PolyAgri®, no color change of the yellow is visible to the naked eye, only a few traces are visible in colorimetry. This is confirmed by comparing the affected surfaces: 80% in the first case and 0.4% in the second case.
Although both suits are certified ISO 27065 (protection against phytosanitary products), it is noted that the filtering PolyAgri® protects much better against vapors and spray aerosols. This is due to the filtering aspect of the textile, which allows better distribution of absorbed products during movements, good interface management, and reabsorption of toxic gases by the carbon lining.
Conclusion
1°) All filtering suits from Ouvry behave similarly. The contaminated air absorbed outside is filtered by the activated carbon microbeads. The toxic substance binds to the carbon and if it has escaped direct filtration, it is trapped by the carbon from the inside (the chemical molecule’s affinity is greater for carbon than for skin); 2°) During movements, air enters over the entire surface without overpressure, and toxins are trapped while in a sealed garment, air passes forcefully at the interfaces and severely contaminates the individual despite the so-called airtight closure of the suit (pumping effect); 3°) The system works even if the fabric is wet; 4°) The interior air is regularly renewed, moisture is removed from the skin, which constantly cools, allowing effective thermoregulation; 5°) These PPEs are washable and reusable; 6°) External heat is better tolerated and the rotation of personnel on the ground is therefore less frequent.
Not only do NRBC filtering suits protect better than Type 3 suits, but they are also physiologically more tolerant and robust. Filtering solutions, therefore, offer the best compromise of protection/mobility/robustness, reducing personnel rotations and the number of suits needed in ramping up a rescue system.
In short, filtering suits are more efficient (no pumping effect), more comfortable (allowing skin cooling), reusable (less waste and therefore more ecologically satisfying), and also mean fewer personnel changes on long missions.
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