Air quality design considerations in industrial and commercial buildings
An introduction to the Industrial HVAC Design Guidelines for Commercial HVAC Design Engineers
- Understand how IAQ/EAQ design features in commercial buildings can be used in industrial facilities.
- Identify the various governmental and third-party agencies that provide guidance for industrial facility design.
- In commercial buildings, the focus of HVAC design is on the health, safety and comfort of the occupants, whereas in industrial buildings the focus shifts to the production process while still prioritizing occupant safety.
- Many industrial facilities will often have stricter guidelines dependent on the kind of product being made.
The majority of heating, ventilation and air conditioning (HVAC) design engineers are familiar with the importance of indoor air quality/indoor environmental quality (IAQ/IEQ) in commercial buildings. These two criteria in commercial buildings primarily focus the design effort on the health, safety, and comfort of the building occupants.
Designing commercial building HVAC systems well requires a thorough understanding of ASHRAE Standard 62.1: Ventilation for Acceptable Indoor Air Quality relative to ventilation requirements, ASHRAE Standard 55: Thermal Environmental Conditions for Human Occupancy for indoor comfort conditions including air movement and how humans react to temperature and humidity and the International Green Construction Code. Much of this experiential knowledge also relates to many of the key IAQ/IEQ considerations in industrial manufacturing and packaging facilities.
The design of industrial facilities focuses primarily on the process being carried out more so than on the comfort of occupants running or monitoring the processes, though the latter is still important. Industrial facilities, such as chemical processing, food production, packaging and warehousing, consumer product manufacturing, or a combination of these operations, tend to give primary attention to temperature, humidity and the presence or concentration of certain gases that affect the processes occurring in the building. However, even in such settings, occupant safety is the one design consideration that takes precedence over the production process. Especially within the IAQ/IEQ realm, hazards to occupant respiration are the top priority.
In specialized industrial facilities, such as pharmaceutical production, chip-set fabrication, biological testing or biologic production facilities, the design may also need to address the cleanliness of the ambient production environment with stringent requirements on the acceptable quantity and size of particulates in the air. When the manufactured product can be microscopic in scale, such as with computer chip set integrated circuits, the presence of otherwise negligible dust and lint particles may invalidate the product being manufactured.
In certain classes of drugs that are injected directly into the body, or in the production and laboratory testing of gene and cell therapy lines, the concerns extend beyond the particulates to encompass pathogens that might be carried into the process on those airborne particles.
Overall, the concerns for indoor air and environmental quality within industrial facilities can have much greater stakes than in commercial buildings. Where the impact in a commercial facility may extend to hundreds or thousands, of occupants and their comfort, the impact in an industrial facility can affect tens of millions of consumers. Additionally, the economic and reputational cost to manufacturers can be astronomical.
Commercial building design guidelines
The ultimate goal of IAQ/EAQ design in commercial facilities such as offices, malls, educational facilities and transportation centers is to engineer a healthy, comfortable environment for human habitation within the building. ASHRAE Standard 62.1, ASHRAE Standard 55, the International Green Construction Code and other standards, guidelines and codes serve as a yardstick, prescribing the minimum acceptable IEQ/IAQ criteria or enhancing them.
In addition to direct air and environmental impact, overall IAQ/IEQ must also address indirect impacts including the energy efficiency of the equipment creating the acceptable indoor conditions. Thus, compliance to ASHRAE Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings, is an integral design aspect of the overall design as well.
As responsible design professionals implementing the aforementioned features in the design of buildings, it is imperative to focus on the following key elements, provided by Whole Building Design, as applicable:
- Adequate indoor air quality through filtration and quantity of ventilation air supply and exhaust for acceptable indoor air quantity
- Temperature and airflow controllability for thermal comfort
- HVAC systems that manage moisture sources and provide indoor humidity control
- Achieve indoor environmental quality through the design of efficient systems, construction adherence to design documents, commissioning, operation and maintenance practices
- Designing a properly illuminated environment per Illuminating Engineering Society (IES) recommendations
- Designing energy efficient systems relative to the use of individual spaces or buildings
- Provide for high-quality, potable water
Industrial building air quality guidelines
In comparison to occupant-centric commercial IAQ/IEQ design, the primary focus of industrial design is on the manufacturing process, as it can potentially affect the quality and consistency of mass-produced products. Deviating from product criteria due to unacceptable variations in IAQ/IEQ can cause entire batches of product to be out of acceptable specifications, thus invalidating massive quantities of product that may cost millions of dollars in raw material, production labor, packaging or materials. In industrial processes like chip fabrication or pharmaceutical drug manufacturing, being out of mandated tolerances, even for short periods of time can have catastrophic economic impact to the business and end-users.
Occupational Safety and Health Administration (OSHA) has established average exposure limits for acceptable levels of contaminants, temperature or humidity for humans over an eight-hour window. However, industrial processes generally do not have such tolerances since the products are precisely measured and processes are developed for producing consistent, uniform and safe products in mass quantities. Fluctuating environmental conditions can lead to product specification or quality variability, which is unacceptable. When sterility is an additional requirement, any duration of exposure to pathogens beyond limits can also void the entire process, cause serious harm and be fatal to end users.
The key design elements for good industrial IEQ/IAQ design include the following:
- Adequate quality and quantity of ventilation air supply and exhaust for acceptable indoor air quantity
- Temperature and airflow controllability for stable process and production consistency
- HVAC systems that maintain hygienic zoning, proper management of moisture sources and adequate indoor humidity control
- Achieve indoor environmental quality through the implementation of good manufacturing practices (GMPs), construction adherence to design documents, commissioning, operations and maintenance practices
- Designing a properly illuminated environment per IES and production specific requirements
- Designing energy efficient systems relative to the use of individual spaces or the building as a whole
- Provide for high-quality, potable water
- Facilitating the production process to operate in as hygienic and sterile environment as required to ensure the highest quality end product
- Maintaining an acceptable level of airborne contaminants by controlling their entry and removing them from the production environment.
Depending on the type of industry and the product, the level of implementation of design strategies may vary, but the following are common design considerations for most industrial facilities:
Hygienic zoning: This is an operational strategy to segregate various areas within the building into high care, medium care and basic care zones, based on the type of product and by controlling the movement of materials and personnel across these zones based on their risk factors, as shown in Figure 1. The designed system needs to maintain the zone-by-zone segregation through appropriate air filtration and pressurization. Controlled transitions zones and drop zones keep the flow of air from high-risk areas to low-risk areas can be done with controlled transitions zones and drop zones. Parts of the building where production doesn’t occur are designated non-GMP areas.
Dilution ventilation and local exhaust: For worker protection in industrial facilities, there are two basic types of ventilation systems — pollutant dilution and local exhaust. Dilution ventilation mixes large amounts of clean, outside air with process air to keep the concentrations of contaminants below the allowable limits set by industrial hygienists. Local exhaust systems are designed to capture contaminants at the source and remove them from the workspace through a ducted system. An industrial plant typically has both systems, with greater emphasis on one or the other depending on the hazard risks of the contaminants. The health hazard potential of an airborne substance is characterized by the acceptable time weighted average threshold limit value as published by American Conference of Governmental Industrial Hygienists (ACGIH) or permissible exposure limit per applicable OSHA and industry standards.
Process air movement: In addition to worker safety, there are also considerations for the production process. For most industrial applications, the higher the hygiene requirement, the higher the air exchange rate to minimize the concentration of contaminants to the process. Where typical air exchange rates for commercial buildings are six air changes per hour (ACH) for human ventilation dilution, process applications require air exchange rates of 10 ACH up to 30 ACH. Clean room applications require air exchange rates near 50 ACH. The volume of air movement becomes more confined as the environment is subject to more stringent criteria. Otherwise, the absolute air movement quantity in cubic feet per minute become untenable for large volume spaces. Figure 2 depicts air pressurization strategy for air movement in a properly hygienic zoned facility.
Industry regulatory agencies
Responsible designers are expected to be aware of the specific industry requirements pertaining to the process being designed. Following are some of the agencies relevant to industrial processes and their codes, standards and/or guidelines:
OSHA: Under the U.S. Department of Labor, OSHA ensures safe and healthy working conditions for workers by setting and enforcing standards and by providing training, outreach, education, and assistance. Specific to IAQ/IEQ, it has published ventilation standards including the four standards in OSHA Standard 29 CFR 1910.94 dealing with local industrial exhaust systems. Additionally, it publishes Standard 1910 Subpart Z: Toxic and Hazardous Substances, Table Z-1. This publication includes occupational exposure limits (OELs) for approximately 500 substances with either a maximum instantaneous value, a 15 minute time weighted average or an exposure limit — based on an eight-hour time weighted average exposure. OELs for hundreds of additional substances have been adopted by OSHA, The National Institute for Occupational Safety and Health (NIOSH) and ACGIH.
NIOSH: This U.S. Government research agency focuses on the study of worker safety and health, and empowers employers and workers to create safe and healthy workplaces. NIOSH is part of the U.S. Centers for Disease Control and Prevention, in the U.S. Department of Health and Human Services. It has published several useful criteria documents, current intelligence bulletins, reports, fact sheets and impact sheets. These provide technical guidance on controlling worker exposure to airborne contaminants, nanoparticles, tobacco smoke, heat and to various chemicals and biological agents.
ACGIH: The ACGIH Industrial Ventilation Committee publishes “Industrial Ventilation, a Manual of Recommended Practice for Design.” This manual is recognized worldwide as one of the key design guides for all aspects of industrial ventilation design and applications. The topics covered include equipment fundamentals, associated system design, local exhaust system design, general industrial ventilation principles and design, supply air system design and special design considerations. The manual compiles references and aggregates data, recommended practices, and code references from many different resources into one compendium.
Additionally, ACGIH publishes an annually updated version of a booklet of threshold limit value occupational exposure guidelines for more than 700 chemical substances and physical agents. There are also more than 50 biological exposure indices that cover more than 80 chemical substances. ACGIH also publishes the Guide to Occupational Exposure Values, which supplements threshold limit value and biological exposure indices exposure guidelines with an accessible reference of the most recently published values.
Prioritizing IAQ/IEQ considerations in both commercial and industrial setting is vital. The former places more emphasis on the occupants’ health and comfort whereas the latter places it on maintaining precise conditions to ensure product quality and occupant safety. Compliance with standards and guidelines such as ASHRAE, ACGIH and OSHA, are essential to create safe and efficient industrial environments. Incorporating the appropriate design approach with adherence to industry-specific requirements is the key to a safe, sustainable and successful industrial environment while safeguarding the health and well-being of workers and consumers.