Hardened protective shelters, such as IS 19079: 2024 (based on ISO 22359: 2024), provide comprehensive specifications for the design, construction and operation of shelters to meet a range of hazards, including explosions, radiation, toxic chemicals and biological agents. This Indian Standard which is identical to ISO 22359 : 2024 ‘Security and resilience Guidelines for hardened protective shelters’ issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on the recommendation of the Risk Management, Security and Resilience Sectional Committee and approval of the Management and Systems Division Council.

What is a Hardened Protective Shelter?

A hardened protective shelter is a strong structure designed to offer shelter and safety during hazardous circumstances.

Unlike temporary disaster shelters such as tents or tarpaulins, these hard shelters are permanent and are built to endure major environmental threats. Its main objective is to ensure the survival of civilians during chemical, biological, radiological or nuclear (CBRN) attacks, natural disasters (earthquakes, floods, storms) and explosive events.

The unpredictable nature of natural disasters, as well as the threat modelled by man-made disasters, has drawn attention to the need for resilient infrastructure capable of protecting lives and critical assets. Hardened protective shelters are an essential component of emergency preparedness. Designed extensively to provide safe shelter in extreme situations, these shelters play an important role in ensuring survival of refugees when conventional structures fail.

The defining characteristics of these shelters are the capability to endure extreme external forces (such as blast waves or seismic shocks) and the ability to uphold breathable air and safe environmental circumstances in dangerous environments. These shelters are often blast-resistant, gas-tight, and self-contained, capable of providing essential resources such as air filtration, overpressure storage, and water, food, and medical supplies.

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Scope of Hardened Protective Shelters

The scope of IS 19079: 2024 covers a wide range of design, construction and operational parameters mandatory for shelters with the objective of providing space safety in a wide range of disaster conditions. These contain natural dangers, such as earthquakes, floods and extreme weather events, along with man-made threats such as chemical, biological, radiological and nuclear (CBRN) attacks, explosions and terrorist activities.

The standard summaries the technical provisions for the types of shelters and their envisioned purpose, confirming that each shelter is furnished to meet the specific requirements of its users in an emergency situation. This scope includes general design parameters, operational modes ((such as filtration mode, by-pass mod, and elevated readiness mode) and maintenance and cost-effectiveness guidelines. The document also states the size, function, and security level of shelters. 

This standard applies to shelters designed to protect civil defence and critical infrastructure, as well as military assets and civilian operations. However, the scope of shelter requirements for army uses is limited, as it is governed by the Geneva Conventions or civil protection standards. 

The scope is to ensure that shelters offer effective protection for both individuals and acute infrastructure during an extensive variety of emergency circumstances, with long-term survival capabilities and the ability to acclimate to evolving threat conditions.

The Importance of Hardened Shelters in Disaster Preparedness

Disasters such as, Earthquakes, hurricanes, natural disasters, low-layer nuclear accidents, terrorism, man-made hazards, and other global risks hardened shelters serve as a critical element in disaster resilience. They guarantee that citizens have a safe abode to live in during catastrophic events. These shelters can expressively minimize casualties and prevent long-term damage to affected inhabitants. Apart from this, these shelters serve not only the civilian population but also critical infrastructure such as command centres, data storage facilities and industrial assets. While protecting these crucial functions, shelters help in maintaining security, stability, and the well-being of the wider society even when the broader society is under danger.

Key Considerations for Designing Hardened Shelters

Designing a hardened shelter includes more than a reinforced building. Many factors need to be carefully considered to ensure the efficiency and effectiveness of a shelter during a disaster. IS 19079: 2024 summaries a number of parameters that must be considered during the design and construction stage. 

General Parameters for Shelter Design

• Purpose of the Shelter: Shelters should be designed keeping in mind their intended use, be it civilian protection, industrial property protection, or military infrastructure. Each type needs a different approach to security, capacity and efficiency.
• Local Environmental Conditions: Local climate and geography play an important role in defining the capability of soil to endure natural forces such as rainfall, seismic activity, and weather.
• Capacity, Volume, and Floor Space: The capacity of the shelter should be judged based on the number of people who need to maintain the shelter, as well as how much space each resident needs for comfort and safety. 
• Potential Overcrowding: Designers should plan for the possibility of overcrowding, ensuring that additional people can be accommodated without compromising security during a shelter crisis.
• Occupant Activity Levels: It is important to design proper ventilation systems and ensure that shelters are well ventilated keeping in mind the expected activity levels of residents.
• Protective Functions: The shelters should be designed with safeguarding purposes in mind, like there must be air filtration, thermal insulation, radiation shielding, and can provides protection against any outside dangers. The level of protection required will rely on the kind of threat the shelter is designed to uphold. 
• Habitability Criteria: Air quality (CO2 and O2 concentrations), temperature, humidity and the rate of air change are important factors that need to be carefully controlled to ensure long-term survival of sheltered residents.
• Life Cycle Management: Shelters should be designed with maintenance, durability and repair in mind, to ensure that they are functional and safe for long-term use. 
• Cost-Effect Analysis: The shelter’s design and construction should provide a cost-effective solution that balances quality and affordability, ensuring optimal functionality within budgetary constraints.

Also Read: IS 19085: 2024 - Glass Containers for Homoeopathic Pharmaceutical Preparations - Specification

Types of Hardened Shelters

IS 19079: 2024 outlines a number of types of shelters based on their envisioned purpose and occupancy capacity. These include:

• Small Shelters: They are designed to protect the inhabitants of a single residential building or a small community, small shelters usually accommodate up to 150 people. They are typically constructed from reinforced concrete and are ideal for localized emergencies.
• Medium-Sized Shelters: These shelters are designed for larger residential or commercial establishments, such as office buildings, shopping malls, or hotels, with a capacity of up to 1,000 people. Like small shelters, they are often made from reinforced concrete and provide protection for both residents and visitors.
• Large Shelters: Large shelters can accommodate up to 10,000 people and are typically designed to protect entire districts or communities. They are often built into bedrock or reinforced concrete to ensure they can withstand major threats.
• Shelters for Civilian Assets and Functions: This approach focuses on the security of critical infrastructure such as command centres, data centres and utilities. The priority of the eight design here is less about the number of occupants and more about ensuring that the critical functions of the shelter remain operational during a disaster.
• Shelters for Military Assets: These shelters are designed to protect military equipment and infrastructure, such as weapons and vehicles, although they are outside the scope of civilian protective shelters according to the Geneva Convention.

Operational Modes: Filtration, By-Pass, and Elevated Readiness

The performance of hardened protective shelters is also linked to operational modes that control how well they respond to specific threats. This mode confirms that the shelter can adjust its ventilation, air quality and overall safety as the shelter evolves.

• Filtration Mode: The filtration mode is stimulated when the external environment is adulterated with chemical or biological agents or hazardous substances. In this mode, the CBRN filtration system of shelters plays an important role in ensuring the survival of residents.

1. Steps to Enter Filtration Mode: The regular ventilation system is switched off and the emergency ventilation system is activated. The shelter has been adjusted for overpressure and the entrance has been sealed to prevent contamination.
2. Key Considerations: Shelters must be equipped with airlocks and all individuals entering should undergo distillation. Filtering mode should be activated by several teams, it is necessary to communicate with the authorities and keep the residents informed during the whole process.

• By-Pass Mode: After the filtration mode has run its course and the air quality is deemed safe, the shelter switches to the by-pass mode. This mode allows the shelter to bypass the CBRN filtration system and take in a larger volume of air from the outside.

1. Steps to Enter By-Pass Mode: The filtration system is detached, and the shelter’s overpressure system is rearranged to permit for the higher air volume.
2. Key Considerations: Related to the filtration mode, the shelter’s inhabitants must remain well-versed, and preparations should be made for the eventual dissolution of the by-pass mode once it is safe to leave the shelter.

• Elevated Readiness Mode: Once the threat has passed, the shelter is in high-alert mode, and those who are sure that they are needed can be quickly followed in filtration mode. This mode focuses on upholding well- organized shelters while allowing organizing and replenishment of resources.

1. Steps to Maintain Elevated Readiness Mode: The normal ventilation system is switched on, and water, food, and medical supplies are replenished. The shelter is cleaned, and any necessary repairs are made. Pre-filters and CBRN filters are replaced as needed, and personal protective equipment is resupplied.

Also Read: IS 19063: 2024 ISO 22324: 2022 Security and Resilience Emergency Management Guidelines for Colour Coded Alert

Conclusion

Hardened protective shelters represent an important component of disaster resilience. IS 19079: 2024 lays down broad guidelines to ensure that shelters are designed to withstand multiple hazards, including natural disasters and man-made hazards. They guarantee that citizens have a safe abode to live in during catastrophic events. These shelters can expressively minimize casualties and prevent long-term damage to affected inhabitants. The shelters should be designed with safeguarding purposes in mind, like there must be air filtration, thermal insulation, radiation shielding, and can provides protection against any outside dangers. 
As the world faces extensively complex and changeable dangers, the requirement for flexible and well-organized shelters is becoming more and more important in the event of emergencies. Hardened shelter, when accurately planned and implemented, it offers an important resource in safeguarding people's security and survival during a disaster.