Captive Wind -- Part One

This is the first in a two part series on improving indoor air quality, which is a growing health problem in the United States. Part one focuses on air quality standards, contaminants of concern and exposure pathways. Part two, which will appear in our June 2001 issue, will deal with an examination of air handling systems and how they can contribute to poor indoor air quality.

It was the wind that gave them life. It is the wind that comes out of our mouths now that gives us life. When this ceases to blow we die. In the skin at the tips of our fingers we see the trail of the wind, it shows us the wind blew when our ancestors were created. - Navajo Chant

The Clean Air Act Amendments (CAAA) of 1990, Public Law (PL) 101-549 (42 U.S. Code (USC) 7401-7671q), is currently the federal legislation regulating the prevention and control of air pollution in our environment (outdoor air). The National Emission Standards for Hazardous Air Pollutants (NESHAPs) have been established in accordance with the Clean Air Act (CAA) as amended in the CAAA. To date, ambient indoor air quality has not been regulated by a Federal mandate. Industry standards such as those produced by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and American Society for Testing and Materials (ASTM) provide engineers with criteria guidance for air handling and treatment systems. Maintenance and operations to ensure that designed systems continue to deliver quality air are not regulated. Operating procedure changes, altered maintenance priorities and retrofitting of air handling system may contribute to air handling problems. In order to provide replacement or make-up air, a variety of systems are used to move air into and out of a facility. Heat recovery may include systems to conductively channel heat from heating, ventilation and air conditioning (HVAC) systems and service water heating, use of economizer cycles, mixing of reusable air with fresh air and various forms of insulation. Indoor air quality studies should be conducted in conjunction with an evaluation of the current mechanical system usage, operation and maintenance.

To date, ambient indoor air quality has not been regulated by a federal mandate.

Indoor Air

Through standards, regulations and laws, we now attempt to guarantee a certain environmental air quality. We have acknowledged that the air encircling our planet at a depth of several miles is the only source of air we and other oxygen dependant organisms on Earth breathe. The same outdoor issues -- either by transfer from ambient, outside air or through interior operations within a facility -- become a concern to indoor air quality. However, the link between environmental air quality standards and indoor air quality standards may not be readily apparent.

Indoor air problems can cause a variety of detrimental health effects. The use of source reduction, air handling systems, filtration and sanitation methods to improve indoor air quality may prevent or ameliorate some of these effects, but the continued coordination of engineering and public health methodologies is required to design better buildings and better methods to maintain adequate interior air.

Environmental Air Quality Standards

The CAAA describes air pollution control requirements for geographic areas in the United States with respect to the National Ambient Air Quality Standards (NAAQS). The following air pollution concerns are regulated in the context of the CAAA:

  • Motor vehicles as sources of pollutants;
  • Routine industrial emissions of hazardous air pollutants;
  • Accidental releases of highly hazardous chemicals (Risk Management Program/Plan development);
  • Commercial facilities that produce energy for sale are addressed in terms of acid deposition control (acid rain, acid particulate potential from stack emissions); and
  • Emissions of chlorofluorocarbons (CFC), halons and other halogenated chemicals from various sources (air conditioning systems, aerosol can propellant usage, fire suppression systems).

The CAAA does not guarantee clean air; instead the intent is to provide a benchmark for the attainment of air quality standards for a region, and to determine zones of chemical influence during an accident. These air quality standards do not require clean air in all areas within a region; these standards require collective attainment for the region at large. Federal and state (delegated authority) compliance initiatives may focus on limiting individual sources of air pollution in order to attain these regional goals.

In other words, the air immediately around a source factory or facility can be such that those immediately within this air environment experience poor air quality; however, when this air is mixed with the region's entire air column, the region as a whole has acceptable air quality as measured by the CAAA standards.

However, the definitions used for Clear Air Act Amendment issues may be different from those associated with workplace air sampling.

The National Emission Standards for Hazardous Air Pollutants (NESHAPs) have been established in accordance with the Clean Air Act (CAA) as amended in the CAAA. NESHAPs' definition of a hazardous air pollutant is a pollutant listed in or pursuant to section 112(b) of the CAA. NESHAPs regulates asbestos as well as various volatile organic compounds (VOCs), semi-volatile organics (SVOCs), and heavy metals (i.e., lead, cadmium, mercury).

These U.S. Environmental Protection Agency (EPA) regulations cover the generally available air pollutants that could compromise both outdoor and indoor air quality. Other EPA regulations deal with specific source reduction, emergency releases of hazardous substances and toxic chemical releases associated with construction/demolition activities. Our discussion herein will be limited to outdoor air as an ambient air stream available for indoor air intake and potential effects of supplying already polluted air to an indoor environment.

EPA provides a list of the common air pollutants (criteria air pollutants) and other information in the "Plain English Guide to The Clean Air Act" available at

Contaminants of Concern

Workplace air sampling may be used to determine either ambient (general indoor environ) or point source generated air contaminants. Point source generated contaminants are those produced by specific industrial, agricultural, commercial or other defined work efforts. However, the definitions used for CAAA issues may be different from those associated with work place air sampling.

For example, particulate matter emissions in air 40 Code of Federal Regulations (CFR) 60.2 are defined as any airborne finely divided solid or liquid material, except uncombined water, emitted to the ambient air. This definition is therefor much broader than the Occupational Safety and Health Administration (OSHA) definition. Essentially, OSHA defines particulate in terms of respirator usage as follows: "Particulate-filter respirator. An air purifying respirator, commonly referred to as a dust or a fume respirator, which removes most of the dust or fume from the air passing through the device." For OSHA, particulate refers to dust or fume and not to liquid material.

Even when definitions are consistent, some contaminants have not been quantified as to risk. For instance, biological contaminants (bacteria and molds) are currently not addressed by any EPA standards. The EPA funded research into these issues was published in 1994 as Review of Quantitative Standards and Guidelines for Fungi in Indoor Air. Further work towards EPA regulations addressing biological risk issues has not resulted and a regulatory definition per EPA of quantitative biological risk has not been established for most biological contaminants.

A regulatory definition per EPA of quantitative biological risk has not been established for most biological contaminants.

Indoor Air Quality Standards

The work force and its air quality is addressed through OSHA's permissible exposure limits (PELs), whereby OSHA establishes a limit on certain chemicals in the work place. These limits do not apply to sensitized individuals, the immune compromised, the very young or the very old, and, in some instances, may be gender specific. Gender specificity implies that PELs and the research on which PELs were based may not be protective of men or women in certain stages of life, especially as regards reproductive potential.

To date, ambient indoor air quality has not been regulated by a federal mandate. Industry standards such as those produced by ASHRAE and ASTM provide engineers with criteria guidance for air handling and treatment systems. These standards are primarily focused on initial design efforts whether for new building construction or retrofitting of building components.

Maintenance and operations to ensure that designed systems continue to deliver quality air are not regulated. Industry standards and good practice doctrines provide some guidance. Still, real world maintenance and operations are largely determined by the interpretation and implementation of specified requirements at the facility. Thus, a system originally designed to maintain a certain makeup air inflow may/may not be operated and maintained to continue providing that airflow. Operating procedure changes, altered maintenance priorities, and retrofitting of air handling system may contribute to air handling problems.

The lack of indoor air quality standards for general building usage was the impetus for OSHA indoor air quality rule making. In Talking Points for Assisstant Secretary Dear Rev. 6/17 Communications Workers of American Intl. Occupational Safety & Health Conference 9:00 a.m. Thursday, June 9, 1994; the following Indoor Air Quality (IAQ) initiatives were expressed, "We have stepped up to a big health problem and published a proposed rule that would regulate indoor air quality and environmental tobacco smoke to protect more than 20 million exposed workers. We have taken the action to prevent thousands of heart disease deaths, hundreds of lung disease deaths, and respiratory diseases and other ailments linked to these hazards. The environmental tobacco smoke provisions would apply to more than six million enclosed and indoor workplaces under OSHA jurisdiction, while the indoor air provisions apply to more than 4.5 million non-industrial work sites. Hearings are to begin in the fall."

This proposed rule is the not yet finalized indoor air quality regulation developed by OSHA. OSHA's proposal focused on:

  • Maintenance and operation of HVAC systems to reduce health effects related to indoor air pollution;
  • Provisions for the control of specific contaminant sources (i.e., environmental tobacco smoke (ETS), bacteria, molds, VOCs; and
  • Training and recordkeeping requirements

The administrative record on this rulemaking closed on February 9, 1996. Since the inception of this regulation, various proponents and challengers continue to question the need for this regulation, and the finalization date continues to be unknown.

Indoor Air and Biology

The burning of fossil fuels and improper sanitation makes some of these problems no different than those faced hundreds of years ago. The manner of transmittal may be different with our aluminum ductwork and digitally controlled logic systems to regulate airflow, but the basics are the same. The human organism when breathing smoke, heavy metals, semi-volatile and volatile organic chemicals hour after hour will suffer some level of respiratory irritation or other health effect. These effects may be subclinical and therefor may go unnoticed.

The body tries to rid itself of foreign airborne solids (particulates and metal fumes), liquids (vapors, mists) and gases by one of the following means:

  • Entrapment in nose hairs, and/or cilia located within the trachea;
  • Flushing out of particulate by washing the nose and trachea with mucous to agglomerate particulates for more ready removal;
  • Coughing, sneezing and coughing spasms;
  • Scar formation using fibrous structures and sometimes encystment of the scared area as the center portion fills with fluids;
  • Action of white blood cells throughout the contaminant route, including phagocytes that ingest the contaminant in total and there-by wrap themselves around the intruder;
  • Metabolic and immune processes for contaminants that leave the lungs via blood and lymph systems; or
  • Filtration of blood within the lymph nodes, spleen and kidneys.

During this interval of time as contaminants are being acted upon, the old adage "The dose makes the poison" is often true. For children and immune compromised individuals, even a lesser dose may cause irreparable harm. We often tend to think in terms of immune compromised individuals as only those with a deadly disease or suffering with the effects of chemotherapy; however, all of us go through immune system cycles where we become temporarily compromised. At these times, even the so-called normal, healthy individual may become sensitized to contaminants or suffer toxicological effects beyond those normally expected.

Given the limitations of the human sensory system, source reduction devices must be monitored by more than just sensory input.

Some contaminants have extremely acute (within hours) and/or chronic effects (within a day or more). These contaminants are some of those quantified by the OSHA PELs and the CAA NAAQS. However, we do not know enough about the human body or the wide range of chemical interactions to have quantified all exposure potentials or their effects. Even the OSHA PELs are based not on total lack of effect through exposure -- rather PELs are based on the assumption that within 16 hours the worker will recover, in time for the next day's work.

Source Reduction and Exposure Pathways

While we await the unraveling of all the human genome mysteries, and the assessment of all known chemicals, we do have some tools to make these situations better. If we use the following as an ideal model: temperature around 70 degrees Fahrenheit, humidity 60 percent, no visible dust, no industrial sources, no burning of fossil fuels, no intrusion of biologicals from molds to rats, then we can make some very idealistic projections. The challenge is to approach this model given the realities of life.

Source reduction may involve adding more ventilation systems and enclosing the areas where contaminant generation is occurring. One of the initial advantages of any closed duct or closed area ventilation system is that the source of heating and cooling may be located separate from the living spaces.

In areas of the world where heating still requires burning fires in the interiors of homes and workplaces, the potential for the periphery of the fire event to off-gas chemically intact toxic materials must be considered. For children living in these homes day after day, the cumulative result may be increased incidence of asthma and other respiratory diseases.

Industrial usage of chemicals that foul the environmental air stream may further potentiate any residential risk. The particulates carried home by adults and children working outside the home may include lead, asbestos, polynuclear aromatic hydrocarbons (PAHs), dioxins and other semi-volatile organics laced to soil particulates. Both the workers and those who live with them may be exposed. In private residences in the industrial world, a hidden source of exposure exists when clothes washing is accomplished a few feet from the furnace systems that deliver air to our homes. Dust laden clothing can contaminate these air delivery systems. Heavy metals, like lead, and asbestos may enter the air ducts relatively unchanged even after going through a combustion event in the furnace interior.

Biological exposures that contaminate building interiors have an added hazard potential -- biological risk can amplify through reproduction both in our homes, industries and in us.

Chemicals such as mercury will disperse through off-gassing at the liquid to air interface. With increases in available surface area by mechanically breaking apart mercury pools (spillage, vacuuming events), additional off-gassing will occur. Continual chemical exposure may be possible from drains, plumbing junctures, cracks in floors, behind baseboards and associated with porous building materials, such as carpet.

Gases and volatile organic, especially those we are capable of smelling -- may ultimately be the least problematic -- as a harsh smell will usually be a call to action. However, some of the most toxic volatiles have no smell. Other volatiles cause increased desensitization of either the olfactory nerve or the interpretive regions of the brain, and workers or other exposed individuals no longer notice these chemicals. These desensitization phenomena can occur very rapidly -- remember the last time you put on too much cologne? Unfortunately our brain has a long list of bad smells and yet may not be programmed for certain industrial chemicals -- leading to an incorrect warning response.

Given the limitations of the human sensory system, source reduction devices must be monitored by more than just sensory input. Modern logic control systems and contaminant detection systems serve to monitor day to day operation of the more sophisticated systems. All too often these systems are juxtaposited with the in-place older systems, and adequate monitoring is not occurring. In-place monitors are also subject to degradation and all chemicals cannot be monitored via this method.


Agency for Toxic Substances and Disease Registry --

U.S. EPA Integrated Risk Information System --

U.S. EPA National Center for Environmental Assessment, Particulate Matter --

Liftoff to Space Exploration, Earth's Atmosphere

American Society of Heating, Refrigerating and Air-Conditioning Engineers Inc. --

U.S. Army Corps of Engineers, Hazardous, Toxic and Radioactive Waste Center of Expertise --

This article originally appeared in the May 2001 issue of Environmental Protection, Vol. 12, No. 5, p. 16.

This article originally appeared in the 05/01/2001 issue of Environmental Protection.