Tokyo sarin attack of March 20, 1995: a major turning point in CBRN risk management

1. The chemical attack on the Tokyo subway

On March 20, 1995, five members of the cult Aum Shinrikyo simultaneously released sarin gas on board trains running on three subway lines converging toward central Tokyo. The agent was placed in plastic bags that the attackers punctured before leaving the trains. Vapors rapidly began to affect passengers. As the trains continued along their routes, poisoned passengers disembarked at successive stations, spreading contamination throughout the subway network. The attack resulted in 13 deaths and more than 5,000 injured.

Tokyo subway attack of 1995 Workers cleaning a train car after members of AUM Shinrikyo released sarin in the Tokyo subway system, March 1995

2. Sarin: a fast-acting, highly dangerous nerve agent

Sarin (or GB) is an organophosphate classified among nerve agents. It causes continuous stimulation of the nervous system. Extremely lethal yet non-persistent, it is soluble in water and most biological fluids. Although it can be absorbed through the skin, the high volatility of this product means that it primarily affects the eyes and the respiratory system (as was the case in this attack). Most victims suffered from breathing difficulties, miosis, and visual disturbances. Symptom severity depended on the dose inhaled, duration of exposure, and proximity to the source.

3. Crisis management revealing a lack of preparedness for chemical threats

This was the first CBRN attack of such magnitude. Its management exposed the lack of preparedness of emergency services at the time. Tokyo’s fire department had no capability to identify or treat sarin. First responders wore no personal protective equipment; masks were distributed only about forty minutes after operations began. Confirmation of sarin use took several hours, delaying decontamination measures. Numerous cases of secondary contamination were observed among first responders and hospital staff.

Symptoms presented by victims arriving at hospitals were often misinterpreted due to lack of information, and appropriate treatment was not immediately administered.

4. The emergence of international reflection on CBRN response

The attack highlighted the severe consequences of lacking an operational doctrine adapted to chemical attacks: difficulty identifying the agent, exposure of first responders, secondary contamination, and disorganized hospital care. These shortcomings underscored the need for clear, shared, and immediately applicable procedures. Significant efforts were undertaken worldwide. Countries established specialized CBRN response teams, and major cities developed chemical detection capabilities.

5. Lessons learned in France: toward a structured doctrine

In France, a delegation from the Direction de la Sécurité Civile traveled to Japan to analyze the emergency response and extract lessons applicable to the national context. This feedback emphasized the importance of coordinated action among all involved stakeholders.

6. Circular 700: the foundation of the French response to chemical attacks

This work contributed to the development and formalization of the French national doctrine. Published in 2008, Circular 700 defines the operational framework for responding to terrorist actions involving chemical agents. It notably recommends:

• establishing protection zones to limit the spread of contamination and prevent secondary exposure
• conducting emergency decontamination
• observing and recognizing clinical signs to identify the class of toxic agent and promptly adapt medical care
• triaging victims according to symptom severity to prioritize treatment

All these measures rely on the use of CBRN personal protective equipment, including:

• a CBRN protective suit
• a mask fitted with an appropriate filter canister
• gloves
• boots and/or overboots

7. The evolution of CBRN protective equipment: a graduated approach

Circular 700 remains the current reference for the French national doctrine governing emergency and medical response to terrorist incidents involving chemical materials. It was updated in 2018, with changes focusing particularly on recommended protective clothing and equipment for CBRN operations. The updated version promotes a graduated approach: the choice of protective equipment must be adapted to the nature of the risk and the zoning in place.

This evolution has encouraged the use of air-permeable filtering suits. Unlike the impermeable suits explicitly cited in the original version of the circular, filtering suits allow rapid dissipation of heat and perspiration while maintaining strong operational performance. They provide greater wearer comfort and enable longer intervention times. Moreover, filtering suits facilitate the implementation of reflex zoning—one of the very first steps in the operational framework—by allowing rapid, safe, and proportionate entry into a suspected but not yet fully characterized environment, prior to formal identification of the toxic agent.

8. 1995-Today: a modern, coordinated, and operational CBRN doctrine

The sarin attack carried out in 1995 on the Tokyo subway marked a turning point in the contemporary history of CBRN crisis management. The lessons learned led to the development of a structured and evolving doctrine that incorporates advances in operational capabilities. Modern CBRN protection now relies on the combination of clear procedures, detection capabilities, appropriate equipment, and close coordination among all actors to ensure rapid and safe interventions.