Collective Protection

TRIPLEX 2004, Starrum - Norway; Assistance and Protection Exercise.

Source: A FOA Briefing Book on Chemical Weapons.

Protection against CW agents can be arranged for individuals by means of a protective mask and special clothing. In many cases, a group of people can use collective protection, e.g., vehicles or special shelters.

 

Collective Shelters

  • People under a roof, e.g., indoors or in covered vehicles, are not only protected against CW agents in liquid form but also receive a certain degree of protection against aerosols and gases since the air turnover in such spaces is lower. The concentration increases more slowly and there is not such a hurry to don protective masks.
  • The air supplied to shelters is purified in much the same way as in protective masks. The air is drawn through an aerosol filter and a layer of active carbon by means of a fan.
  • Temperature is the limiting factor for the period of residence in a shelter. The more people present the faster the temperature will rise. Normally, some of this heat is removed by conductance through the walls, floor and ceiling of the shelter as well as through continuous ventilation. The capacity of the ventilation system is adapted to make the climate endurable during different times of the year and with a normal load.
  • Ventilation with filtered air in normal individual shelters is calculated to be 1.5-3 m3 per person and hour. In more important and larger shelters, there are two ventilation systems - one for use during peace-time with a relatively high air turnover, up to 10 m3 per person and hour, and the other for use in CW-attacks with filtered air.
  • The time that can be spent in a shelter when the ventilation system is shut down is limited by the decreasing oxygen concentration and the increasing concentration of carbon dioxide in the air. Approximate limits for survival can be placed at 15-13 per cent for oxygen and 4-6 per cent for carbon dioxide. These limits are reached almost simultaneously after ca. 6-8 hours in cases of normal occupation (each person with a floor area of 0.75 m2 and a ceiling height of 2.2 m).
  • Bearing in mind these conditions, it is important to try to use the peace-time ventilation with high turnover of air as long as possible. Advance warning of attacks must then be given in sufficient time to enable the occupants to change to CW ventilation.
  • Requests by personnel exposed to CW agents wishing to enter the shelter during a CW attack or later will imply a difficult problem. The people already in the shelter will be exposed to major risks if anybody attempts to pass through the gas-lock from an area exposed to persistent CW agents. If this must be done, such persons must be first decontaminated and the decontamination result checked.

Did You Know?

A warning system for CW agent attacks can consist both of sirens in urban areas and of warnings on the radio.

The civil defence organization could equip special patrols for detection and relief in environments contaminated with CW agents.

The civil defence can also have the responsibility for informing the general public when it is risk-free to leave shelters, to air apartments, etc.