Objective

Following the release of a CBR chemical biological radiological agent urgent controls are required to prevent that contamination from entering or dispersing throughout a building where it may affect the occupants. Safety and employer liability may be a strong drivers but the cost of decontamination and business disruption are equal components. The basis of all risk control is to remove or mitigate the hazard and the cbr-response plan identifies your best route to this end.

All buildings have some form of control available. This can be as simple as doors, windows or as complicated as recognising the effects of pressure plain or stack effect. Equally buildings have distribution devices in which cbr elements can be driven through buildings at varying speeds. The objective is to utilise all current and available controls and adapt for the control of the environment which in turn will control cbr ingress or distribution. 1. Ventilation Supply System

This section identifies the possible use of HVAC systems in varying situations. It also identifies the potential for egress of CBR contaminate. It should be recognised that to turn off HVAC systems does not necessarily mean close them and integral or associated ductwork.

2. Negative Pressure Points

Extract systems, apart from normal ventilation systems can become a useful tool in providing pressure differentials, zoning and additional extraction of contaminates. As with ventilation systems the effect of turning off a system does not necessarily mean the closure of the system and contamination may enter. This section identifies potential use of extract systems. may become a viable ingress route for both internal or external contamination.

3. Filtration

HVAC systems which provide air distribution throughout buildings are protected by air filtration usually pleated, boxed or cartridge or roller filters. Some are protected by HEPA filters. This stands for high extraction particulate arrest, and captures 99.97% of all particulates down to .3 of a micron. Hepa will not capture gas or chemical agents and carbon filters should be considered for this application. You should be aware that Hepa or carbon filters require specially designed filter mountings to prevent leakage or by pass, and the fan units are specially designed to overcome the higher level of filter resistance. Two types of Hepa must be considered, those, which filter all incoming air, and those, which filter all supply air. Where the AHU fitted with the Hepa system forms an integral part of supply and extract upto 98% of extract air can be remixed with only 2-5% fresh or make up air. This means any contaminate which is circulating within the building may become extracted from the incident area returned to the AHU, and enter the supply side without passing through the Hepa. The second type of filtration is where the Hepa is fitted to the supply and not the intake side of the AHU filter bank. This will accommodate filtration of all extract or re-circulating return air.

4. AHU Air Handling Units

The management of air supply within buildings is governed by legislation, which requires minimum air changes to ensure a healthy environment. The management of air quality is usually attained by a HVAC system, which provides both supply and extract. The fresh air supply is usually maintained at low levels of 2-5% with 95-98% of extract air being remixed with the fresh or make up air. The mixing and supply through ductwork is provided by AHU's air handling units. These units can be independent of each other or combined and may be centrally controlled to increase or decrease mix levels.

5. Zoning Controls

Buildings can vary in design and use with some areas requiring additional or minimal air supply. Equally specific tenants may have altered or improved their own environmental conditions by installing additional HVAC systems. Larger buildings may have separate AHU's providing independent floors with ventilation. Some ventilation systems have automatic or centrally controlled dampers to enable balancing of the supply or extract to limit drafts, dead zones etc. Dampers can also be included in localised ceiling mounted VAV or similar control systems.

6. Temperature Controls

Building heating and climate control is usually centrally operated although various areas can be controlled with the use of independent controls such as VAV, or fan coil systems for air temperature or cassette, for air conditioning cooling systems. This section evaluates the potential to manipulate the building environment but equally should alert the building facility manager that overall contingency plan could be affected if all floors are operated independently. Equally independent controls can, if managed provide localised zoning and controls to manage internal CBR incidents.

7. Evacuation Routes

Evacuation routes can be contaminated and perhaps more importantly a direct route to the outside where contamination may find an easy route in. Equally the various floors can be under different pressures from stairwells and therefore may be a higher risk than contained floors. Lifts can become a pump, , or create vacuums pulling contamination in from outside and distributing contamination both upwards & downwards during use. This section identifies safe evacuation routes or protocol and controls.

8. No HVAC System

This question indicates the limited controls available to reduce or prevent CBR incident effect. It removes some of the options on mitigation or exposure but will place greater emphasis on other controls.

9. IDLH Immediate Danger to Life or Health

This section explores the potential for reducing the impact of a CBR attack. It examines the control or response to IDLH immediate danger to life or health, events and can assist in contingency planning. Response to protect life can be at the detriment to the fabric of the building and the questions raise various pre planning and authorised responsibility issues.

10. Shelter  In Place SIP

Where people are located in a building, subject to varying control factors, identify levels of risk or safety from CBR incidents. The ability to keep out of harms way is at the core of safety procedures and this section identifies areas of protection within your plan. The realistic approach to any cbr event may be to remain in your building until such time as the authorities can assist you in evacuation. This may be period of between hours and days or even weeks.

11. Height of Building

The height of a building can reflect the speed of ingress of a contaminate. It can therefore influence the procedures used to protect the occupants and the variants can impose limitations or benefits in the contingency plans for mitigation or prevention of contaminate ingress.

12. Isolation Parameters

The location and independence of the environment can be influenced by external factors and this section identifies potential ingress points and control measures possible to prevent, mitigate contamination spread or influx.

13. High Risk Areas

Some areas in buildings are at greater risk from the effects of a CBR incident. Typically the post room or reception areas should be considered for additional or independent controls or actions. This section identifies your vulnerability.

14. Evacuation Procedures

This section identifies the safety of occupants and mitigation controls post CBR incident. It explores the protocol assessments of evacuation procedures, routes away from the incident, together with cohort control requirements to ensure occupant safety. The ability to inform and contain occupants where acceptable or demanded to prevent unnecessary exposure and also maintain the safe integrity of the confine, or prevent ingress of contamination. Of paramount importance is the identification of decontamination procedures to limit the effects on personnel following CBR exposure.