Good facility planning and the proper solutions for Heating, Ventilation, and Air Conditioning (HVAC) systems credit today's successful forensic facilities. Together they support modern forensic laboratories by providing comfort for lab occupants and an environment that supports scientific investigation.

They are also critical in maintaining a safe and healthy place of business. The control of temperature, humidity, directional air flow, and air quality are necessary performance factors of the forensic facility’s HVAC system. Working hand-in-hand with that is modular planning, flexibility, human centered design, and sustainability. These are performance factors for the planning and design of the facility. All of these factors must be considered when selecting and designing the air supply and exhaust systems, fixed and movable casework systems, building and safety controls, building envelope and structural systems, central heating and cooling equipment, and construction methods and materials that will not harm the environment. In this two-part article, Ken Mohr and Lou Hartman explore ideas and solutions for your engineering and architectural questions.

A key challenge: Forensic laboratories have a wider range of laboratory spaces than any other type of science facility
Avoid cookie-cutter solutions. That is to say that a generically applied solution throughout the forensic laboratory is one of the biggest mistakes you can make. The only thing generic about a forensic facility is the planning module (building block) set forth to assist in the design, system distribution, and future flexibility of the environment. Designing several HVAC system solutions are necessary to support the wide range of laboratory types. An example would be to compare the ventilation system for a Drug Chemistry laboratory to the requirements of a Ballistics Unit. In this example the two are significantly different. In a Drug Chemistry lab you want to provide ample room air changes per hour (6 to 8, very sustainable; 8 to 12, odor is a bigger issue), but at very low velocities, as not to create air currents that would disrupt an examination process. On the flip side of that is the above average room air changes per hour (30 to 50, aiding in containment of lead) with a directional air flow away or downstream of the occupants in the space. We can also see the differences in the physical space and material selection. The Drug Chemistry lab is a large, open work environment with individual workstations designed for evidence examination while flooded with natural light. The Ballistics Unit test range is a long, narrow space without windows, focused lights on targets, and ballistic resent materials.

A starting precept: Identify and understand the hazards presented in each of the laboratory areas
Don’t assume that a forensic laboratory contains only small amounts of chemicals, so if you classify the building as business occupancy, you’ve done your job. A number of forensic laboratory operations involve some physical or health hazards with daily activates. Materials are used or analyzed that are toxic, infectious, flammable, or explosive. The first step in the architectural design or selection of the HVAC systems comes early in the planning process. Here you have the opportunity to learn not only what is used, but how it is used. The “how” can be more important than how much.

A critical factor in the Latent Print lab is to know if “ninhydrin” is a wet or aerosolized process. Aerosolizing the chemical may cause you to develop the space as a Class 1 Division 1 environment under the electrical code for non-sparking electrical devises. This activity should be contained in a chemical fume hood with a flammable storage cabinet under the fume hood. Remember that a chemical fume hood is a device that is 100% exhausted.

At the same time in Forensic Biology they are working with blood products and no one really knows what is contained in the blood. The best device to exam or prep this product for analysis is a biological safety cabinet. This ventilated device protects the user with an air curtain designed to separate the interior of the cabinet from the exterior environment. It also protects the product from contamination in the same way, but also introduces HEPA (high efficiency particulate air) filtered air from above. Finally this device also protects the environment by filtering and cleaning the exhaust air of the cabinet before it re-enters the room. The air filters on these units remove both odor and particulates of biological materials, not intended for chemical use.

Also in the BSL-3 Lab (biological safety level-3, working with airborne pathogens) investigators are examining an envelope and letter contaminated with anthrax in a glove box. This device is a sealed environment only accessible through a pressurized airlock and thick black rubber gloves bolted into the side of the unit to manipulate the product in the cabinet.

The Basis of Design: A written narrative prepared by the design team, in plain English
There are hundreds of decisions that go into the design of a forensic laboratory. The design team requires input from the scientific staff, the building operations personnel, the lab directors, and those responsible for the project’s financial control. All of these individuals bring a different and important perspective to the decision-making process and managing the communications necessary in making the process a success. The Basis of Design narrative is really a communication tool intended to convey the understanding of the project by the design team to the reader. Those reading the narrative will be making decisions about further funding of the project for construction, operating the facility, and performing scientific analysis on a daily basis. The following outlines the issues found in a typical

Basis of Design:

  • Sighting the facility with consideration for parking, access, landscape, and security
  • Architectural expression, square footage, and materials
  • Modular planning indicating office vs. laboratory unit-by-unit
  • Indoor and outdoor temperature and humidity design conditions
  • Air filtration and special treatment
  • Interior material and finishes for floors, walls, and ceiling
  • Casework systems and laboratory equipment
  • Equipment cooling, electrical, and gases
  • Ventilation rates and pressure relationships for individual spaces
  • Types of chemical fume hoods, biological safety cabinets, and other containment devices
  • The need for standby or redundant equipment and emergency power
  • Monitoring and alarm requirements for critical scientific equipment
  • Provisions for expansion or addition of equipment in the laboratory
  • Strategies for energy conservation, including savings and associated first cost
  • Cost modeling, scheduling, and narrative specifications
  • Graphic image that represents the project

A successful design means integrating the HVAC system with the architectural planning module
Today’s modern forensic laboratories use a system of design identified as modular planning. This approach to architectural space planning reinforces elements of structural design, architectural features such as windows, and the planning of the HVAC systems. Buildings that follow this methodology in planning are inherently more flexible and deliver higher long-term value to the owner. Modular planning is based on developing a planning module that becomes the “building block” for the floor plan. The perfect module is equal in the “x” dimension and in the “y” dimension with the “z” dimension (slab to slab) of 15 ft to 18 ft. Laboratory planning modules are frequently 10 ft to 12 ft wide and 20 ft to 36 ft deep. The HVAC system branches and drops can align themselves along the edges of the module. The laboratory modules can be developed as a single work area creating an exam room or evidence storage; or combine several of the modules together and form a multiple-station laboratory or instrument room. This system of planning does not depreciate the special needs of staff or functions; however, it does take into consideration everyone’s needs and functions to develop a building that will work today as well as tomorrow. By keeping the modules equal they can easily be linked and/or rotated, essentially creating a thousand-piece jigsaw puzzle that fits together resulting in a functioning laboratory. Integrating the HVAC distribution system into modular planning can reflect the architectural planning and increases the systems flexibility well into the future.

Anticipating change: Does science keep pace with the legal environment or can the legal environment keep pace with science?
The United States legal system must deal with a variety of issues concerning scientific evidence; and the legal environment is changing every day all across the country. New laws pertaining to the collection of DNA evidence from non-felons to storage of DNA material; from finger printing bus drivers, hunters, and criminals to maintaining these records for reference. Each new law has the potential of effecting crime lab analyses, case backlog, and storage of evidence. This science is also evolving, becoming more advanced and capable of analyzing finer and finer fragments of evidence. Law enforcement objectives combined with scientific equipment is continually evolving and requires HVAC systems design that accommodates change without modifications. For example, the cooling capacity for an analytical area may need to accommodate a shift to high throughput robotic analytical equipment. Using a 12 ft x 12 ft module will also accommodate the robotic function by providing circulation around the robotics station and support at the perimeter of the module. The scientific advancement of robotics allows for analysis 24/7, bringing cases to the courts faster. Another example may be to size the building exhaust system to allow for additional exhaust devices in the future. As science methodologies change so may the need for fume hoods, biological safety cabinets, snorkels, or glove boxes.

Containing hazards: It is important to protect the staff, the evidence, and the environment from harm
There are a number of devices commonly used in a forensic laboratory to contain potentially hazardous materials and to protect the lab staff, evidence, and environment. These devices include chemical fume hoods, biological safety cabinets, snorkels, flammable storage cabinets, fingerprint dusting stations, evidence drying cabinets, superglue cabinets, acid storage cabinets, and glove boxes. Each device serves a particular purpose to assist the examiner/criminalist with their forensic function. The chemical fume hood is an exhaust device designed to contain odors and vapors protecting the scientist from the activities within by drawing room air past the scientist into the hood and out the building. This device can be wired two ways: where fewer than 10 to 15 hoods exist, each hood could have its own on/off switch allowing the user to control its operation; where more hoods are present, the hoods are controlled by a building management system (BMS). The biological safety cabinet provides protection to the sample under analysis with a curtain of HEPA filtered air—meaning it scrubs the air clean. It can also discharge HEPA filtered air into the room (known as re-circulating) or to the outside (through a hard-ducted or thimble connection). This device is normally plugged in and the user controls the fans’ operation (hard-ducted is through the BMS).

Today there is a wide range of fume hoods and biological safety cabinets available. It is important to disclose to the forensic lab consultant all the functions and processes, chemicals, or biological agents the user intends to use at the exhaust device. Matching the best device to your specific application can save time, money, and lives within the forensic laboratory.

From the design perspective, both chemical fume hoods and biological safety cabinets are large items requiring floor space and can impact the air flow within the laboratory. Location of these devices out of the traffic pattern away from doors and supply air diffusers is very important and assures proper performance. If the potential exists for the air entering the face of the fume hood or the air curtain of the biological safety cabinet to be disturbed, the exhaust stream reverses and airborne contaminants will escape into the laboratory creating a potential hazardous situation.

Other exhaust/safety devices used in forensic laboratories include:

  • Snorkels to remove heat or nontoxic fumes that may be generated from the bench top or analytical equipment.
  • Canopy hoods to capture heat or moisture generated by an autoclave or other scientific process.
  • Fingerprint dusting stations designed to catch the dust in a removable pan and re-circulate HEPA filtered air back into the laboratory.
  • Gas cylinder cabinets allow physical or health hazard compressed gases safe containment and an exhausted environment.
  • Superglue cabinets are designed to allow the user to properly process a latent print and exhaust the ninhydrin gas.
  • Evidence drying cabinets allow evidence to dry in a secure cabinet while ventilated and exhausted through a charcoal and HEPA filter allowing air to be re-circulated back into the room.
  • Flammable and acid storage cabinets offer safe containment of physical or health hazard liquids. Please check local codes, manufacturer’s recommendations, and your insurance policy before agreeing to exhaust these devices. Exhausting would prevent the build-up of potentially hazardous vapors within the cabinets.

We hope that you can find value in combining the design process of architecture and mechanical system design. The benefits of this combined process were explored with aspects of modular planning, exhaust systems, developing the “Basis of Design,” flexibility, and providing a safe environment. These elements are only a portion of the design steps necessary for a successful project. In Part 2 we will continue to explore the issues surrounding forensic facility design.

Lou Hartman is a Principal and Sr. Mechanical Engineer with HarleyEllis, and Ken Mohr is a Principal and Sr. Forensic Laboratory Planner with HERA, Inc. HarleyEllis and HERA together form a strategic alliance called Crime Lab Design, which provides full A/E services for forensic and medical examiner facilities.