Preventing terrorism

The ongoing threat of terrorism in recent years has fuelled considerable research into designing buildings to be as terrorist-proof as possible. Much of this work has looked at the structural aspects of building. However, the anthrax attacks in America and uncovering of a plot in April to use the lethal gas osmium tetroxide against UK targets has focused attention on other weapons in the terrorist armoury – notably chemical, biological and radiological. This has implications for the m&e services.

  It is clear that providing protection against terrorist attacks will only be achieved by taking a holistic approach to a building and its surroundings. New buildings can have anti-terrorist features designed in; there are also things that can be done with existing buildings, though this is more challenging.

In BSRIA’s Technical Note 8/2002: Designing against terrorism, a checklist of the measures that can be taken in the design of a building and its subsequent management highlights the complexity of this issue. It includes the positioning of plantrooms and duplication of plant.

To some extent, the level of security designed into a building will be determined by how likely it is to be targeted, but even low-risk commercial buildings are taking account of the potential for attack. “Buildings are certainly being designed with terror attacks in mind now,” says Kate Millen of consulting engineer Hoare Lea. “One of the things we’ve learnt not to do is move everyone out of the building, because it could be more dangerous outside. There is now greater emphasis on providing safe refuge within the building, either underground or within a hardened core.

“These refuges will have dedicated ventilation, lighting and pa systems with higher resilience than standard systems. Plantrooms serving these areas should also be located in less vulnerable areas of the building,” she adds.

The first line of defence against any airborne attack is to prevent them getting into the building. If they do get in, the ventilation system could help to distribute them, which could have disastrous effects. In America, for example, several buildings were still empty 18 months after being contaminated with anthrax, because the insurers or owners would not pay the huge decontamination costs. In Washington’s Hart Senate building, anthrax spores from a letter opened in one office spread throughout the building via the heating and ventilation system and it took three fumigations to kill the spores. The successful fumigation involved five days of pumping chlorine dioxide gas into the ductwork.

In the US anthrax attacks, the toxic agent arrived via the post room, so in some cases it may be advisable to provide this and other vulnerable spaces, such as receptions, with a separate ventilation system. There is also a case for zoning a building’s ventilation system so spaces can be isolated from each other.

“In the event of a chemical/biological attack you should be able to compartmentalise your building, thereby creating sealed areas into which staff can decant,” suggests John Moore of security adviser MFD International. “This will necessitate knowing how and where the ventilation systems have been installed, and being able to quickly isolate the systems in the event of an attack.”

There are also concerns about biological agents and toxic gases being introduced to buildings via the air intakes or water supply. “Air intakes must be identified and, where appropriate, relocated or the areas around them secured. Likewise, water storage tanks should be housed in a secured, monitored area,” says Moore. “Plantroom areas in buildings, where a lot of the building services plant is exposed, are often very vulnerable places. These areas should be afforded at least the same level of security as the rest of a building.”

In newer buildings air inlets are less vulnerable because it is now standard procedure to mount them high up to avoid taking in traffic fumes. For older buildings where air inlets are at ground level they need to either be moved, which would incur the expense and disruption of re-routing ductwork, or be enclosed to prevent access. Full enclosure would impede the air intake, of course, but it is possible to construct a tall enclosure with the grilles at the top, out of easy reach.

No measures are fully terrorist-proof, so it’s important to look at every aspect of the services to achieve the highest level of protection possible. This means anticipating the worst case scenario, that of chemical or biological agents gaining entry to the ventilation system, and taking the appropriate damage limitation measures, such as providing high levels of filtration. “Increasing filter efficiency is one of the few measures that can be implemented in advance to reduce the consequences of both an interior and exterior release of a particulate chemical, biological or radiological agent,” says the US National Institute for Occupational Safety and Health.

This is not as simple as upgrading to higher efficiency filters, as these tend to have higher pressure losses and will have a knock-on effect on airflows. Where space allows, deep pleated filters or filter banks with a larger nominal inlet area may be feasible. Otherwise, it may be necessary to install additional pre-filtration or change filters more often. The integrity of seals in the filter frame must be checked to prevent unfiltered air bypassing the filters.

All of this has implications for maintenance personnel. In the case of biological agents, the filters may trap them but they won’t kill them, so there is a danger of a filter and adjacent plant being contaminated without anyone knowing. In high-risk buildings, therefore, maintenance staff should introduce safety measures to protect themselves against contamination.

Protective clothing and regular sampling are obvious measures and these can be supplemented with ultraviolet disinfection of the equipment. When using ultraviolet disinfection, it is necessary to take account of the time of exposure to the ultraviolet light, the reflectivity of the surfaces, the possibility of shadows protecting microbiological agents (especially in deep equipment such as heat exchangers), the airflow rate in the space and environmental conditions such as temperature and humidity.

The complexity of the whole issue of anti-terrorist measures means that high-risk projects will normally require input from a specialist. In day-to-day projects there are sensible measures that can be taken and it is likely that building services designers will be expected to anticipate common threats in their designs. Currently, professional indemnity insurance doesn’t cover terrorist acts and, without any test cases, it is difficult to anticipate what countermeasures could reasonably be expected, but it pays to be aware of the risks and act accordingly.