Ebola. Anthrax. Marburg. Hemorrhagic fevers. Until recently, few people were concerned about any of these words. Today, much of the public knows that these are frightening pathogens capable of creating catastrophe if they make their way into our communities.

Highly sophisticated Bio-Safety Level 4 (BSL-4) laboratories must be constructed to study – and to contain – these agents and pathogens. These labs are designed by specialized teams of architects and engineers for the greatest security possible, the toughest protection for the communities in which they are built, and for the safest work environment for researchers.

All laboratories develop unique protocols and standard operating procedures down to the smallest detail. But there are a series of critical design issues – location, security, personnel safety, agent containment, construction and waste removal – that are universal to the security and success of the BSL-4 laboratory.

Every effort is made to prevent the contamination of personnel and to eliminate any possibility of transmitting a deadly pathogen into the community. In fact, these efforts begin even before one enters a BSL-4 facility, with the design and location of the building itself.

Site and Building Security

Every BSL-4 site must prevent intrusion from unwanted visitors on foot or in a vehicle. Ideally, planners vary automobile traffic patterns around the site with trees, bollards, earth berms and other natural barriers to eliminate straight-line access to the building and to prevent direct assault by vehicles. Where possible, parking is far away to prevent a catastrophic car bomb attack from damaging the facility.

Designers also use the most sophisticated technologies available to control the entry of personnel and materials into the facility. These technologies include a combination of electronic (identification cards, key cards), biometric (eye scans, handprint recognition) and manual controls (security personnel at entrances and exits). Only staff members with full security clearance have complete access to the most secure areas. Close-circuit TV surveillance cameras, meanwhile, monitor all activities throughout the facility.

BSL-4 labs present other critical design challenges for architects and engineers. For example, each lab needs a sensitive compartmentalized information facility (SKIF) that shields all critical electronic equipment, wiring and the building itself from outside surveillance, interference and disruption.

Pathogen Containment

BSL-4 facilities are designed as a “box-in-a-box-in-a-box,” creating a cascading group of increasingly secure areas leading to the research lab itself. Only about 25 percent to 32 percent of a BSL-4 facility is dedicated to actual research labs. The remaining space is used for services and systems that support the research. Corridors and support functions wrap around, and service, the research area located inside.

BSL-4 labs are constructed so that absolutely nothing dangerous gets in or out or remains behind. Labs are covered in highly specialized finishes, use specially constructed doors and wall penetration points, and contain a limited number of non-operable windows and other securely sealed, and required, penetration points. Airborne particulates are trapped by a series of high-efficiency particulate air (HEPA) filtering systems. Chemical decontamination removes pathogens from researchers’ protective clothing. Walls are constructed of non-porous materials that are easily decontaminated. And research staff must pass through a series of air locks or bio-vestibules as they move between different “boxes.”

BSL-4 labs generally follow one of two common designs. The first is the “open lab” design, which requires researchers to don protective pressure suits. The other is the “glove box” environment that isolates the lab through a series of negative pressure chambers. The choice of design depends upon the protocols of the specific research being conducted. But both demand the most technologically advanced support systems available.

Open Lab Environment

Open labs are the older of the two designs. The positively pressured suits used by researchers are connected to a life-support system with redundant air compressors and air tanks, alarms, and a HEPA air filtering system. The suits continually push potential airborne pathogens away from the researcher, while cascading negative pressure attracts the potential airborne agents into decontamination exhaust systems. Open labs are more expensive to build than glove box labs because researchers wearing protective suits have restricted movements and need more room to work, and because these labs are equipped with triple redundancy features.

Glove Box Environment

Glove box technology is found in many BSL-4 facilities because it is safe, less restrictive and considerably less expensive to build. These labs can be much smaller than open labs and do not require triple-redundant safety measures. Glove box environments consist of a series of highly secure, sealed stainless steel chambers. Researchers access the chambers through portholes fitted with highly secure and flexible gloves that allow them to easily perform all necessary laboratory procedures.

Only those glove box chambers where agents reside need to be BSL-4-rated environments. Working areas outside the glove boxes can be rated from BL-2 to BL-3. These environments allow staff to wear ordinary lab clothing, easily perform research using the specialized gloves, discuss issues with coworkers, use restroom facilities, and move around freely.

Construction and Support Systems

No matter which environment is chosen, labs must provide the safety of the research staff and ensure the complete containment of material, viral, chemical or nerve agents. The construction specifications required for pathogen containment are a major difference between BSL-4 lab buildings and other lab facilities. Every choice is made to achieve maximum performance.

Each BSL-4 laboratory has a contained air handling system, usually located in the sealed interstitial space above the lab. The air systems are designed for a cascading series of negative pressures culminating in the most negatively pressured area of all – the lab itself. Perimeter areas and corridors are positively pressured to prevent outside contamination from entering the facility. The air, electrical, water, communications, mechanical and other support systems are designed and built with redundancy to ensure continuity should there be an emergency or sudden loss of power.

Typically, BSL-4 lab walls, floors and ceilings are constructed of high-strength concrete. All plumbing pipes, electrical conduits and other ducts are planned and installed before the concrete is poured to eliminate air space around penetration points and to prevent the need for coring into the concrete later. The concrete is cured and dried very slowly – it can take three to six months – to limit cracks and other imperfections. Once fully cured, concrete floors, walls and ceilings are coated with a chemical-resistant epoxy that seals porous surfaces. These specific coatings vary depending upon the agents that will be studied in the lab. The goal is to create a single, continuous surface that can be washed effectively. All work areas, cabinetry and other surfaces are typically constructed of extremely smooth, electro-polished 316 stainless steel that will limit penetration and contamination of research agents and that will be easy to clean.

Safe waste disposal is another critical engineering challenge in BSL-4 lab design.

Liquid waste is usually collected and placed in a kill-tank system – a series of tanks that neutralize and destroy organic material. In the last holding tank, the liquids are tested again and neutralized for correct temperature and pH. Finally, the safe liquids are released into a sanitary sewer system or transported to a remote location for disposal.

Solid waste matter is treated differently. Most often, solid or organic materials are incinerated at extremely high temperatures or neutralized through a plasma-arc system or tissue digester. After being neutralized, these materials can be safely disposed through a sanitary sewer system. In cases where small quantities of solid matter need to be disposed, an autoclave is often used to sterilize the material through a high-pressure, high-temperature process. Properly treating all waste materials ensures that everything that leaves a BSL-4 lab is decontaminated before final disposal.

Research Goals

The goal for researchers is to eliminate the threat posed by the accidental or intentional spread of deadly pathogens. They must be able to work in the safest and most secure environment possible, whether they’re studying deadly agents, creating new diagnostic techniques, or developing vaccines and therapies for exposure. By fully understanding the extraordinary requirements associated with the development of BSL-4 laboratories, architects, engineers and lab experts can design and build the most responsive and secure environment possible, vigorously protect the surrounding community, and help researchers achieve their goals.