ASHRAE Journal - July 2010 - 31

Photo courtesy of HDR Architecture, Inc.; ©W.Scott Chester Photographer

Life safety is a serious concern in a correctional environment because inhabitants cannot freely access means of egress.

that the right decisions are made. Many people are counting pressurization of adjacent spaces and maintaining appropriate on it. pressure differentials are critical to a successful smoke purge For the mechanical engineer, several important factors related system. Often the air-handling unit serving the dayrooms and to their design can compromise security. The first item to con- cells will provide makeup air to the area in a smoke purge event sider is the security level of the facility or the area of the facility: by ramping up via a variable frequency drive (VFD). Other minimum, medium, and maximum security. It is not uncommon times, when the pressure differential is too great, makeup air for a mixture of security levels to exist within the same facility will be supplied via a supplemental makeup unit or louvers that or multibuilding campus, so the engineer must design accord- communicate directly to the outdoors. ingly. The secure perimeter is defined Smoke purge systems should not be by security consultants and/or the staff. confused with an “engineered smoke Air devices are available to the specifier, control system,” as def ined in some appropriate to each security type. Heavy building codes. Engineered smoke congauge steel air devices are typically used trol systems are typically applicable to for all maximum security applications in atriums, rotundas, arenas, and other high cells, particularly when they are in reach volume spaces where the main purpose of inmates. Suicide-resistant grilles can is to maintain a “tenable environment” as be used in psychiatric and other highoccupants egress out of the compartment. risk areas. An engineered smoke control system Hollywood has dramatized jail and requires more calculations and effort on prison escape by way of large sheet the engineer’s part, primarily because metal ducts. This is certainly possible, the authority having jurisdiction (AHJ) and it does occur, but rarely are barrier usually requires it. grilles/bars not specified in all ductwork This type of system is not typically penetrating the secure perimeter walls, applied within a jail or prison because making escape virtually impossible. Grilles and bars usually are specified in all it is not always practical. First, not all Walls to deck and other means of sespaces have combustible materials within ductwork for correctional facilities. curing the construction are carefully them. The contents of individual cells considered during design by security specialists. It is critical for (mattresses, jumpsuits, shoes, bed sheets) are typically made the engineer to work closely with them as the design progresses. of non-combustible, treated materials and fabrics. Most correctional environments do not include many items that would Life Safety contribute to a significant fire or smoke event. Second, many This is a serious subject in a correctional environment because spaces within jails and prisons do not have the volume to all inhabitants cannot freely access means of egress in the event support this type of treatment. For example, most cells have of fire. Many facilities are an institutional occupancy throughout a precast concrete “lid” or a secure ceiling that is usually 8 ft and, as a result, require smoke purge systems that are designed (2.4 m) from the finished floor. With most cells having operto remove smoke, based on detection at a local smoke detector able slider or key-lock doors at 7 ft (2.1 m), it is not practical or in-duct detector. As with most negative-pressure applications, to maintain a developed smoke layer in the space when there
July 2010
Photo courtesy of HDR Architecture, Inc.; ©Mark Trew

Photo courtesy of HDR Architecture, Inc.; ©Tom Kessler Photographer

ASHRAE Journal

ASHRAE Journal - July 2010

Table of Contents for the Digital Edition of ASHRAE Journal - July 2010