No other area in occupational and environmental health has experienced such rapid changes in the recent past as has indoor air quality. Due to an emphasis on energy conservation, buildings are more dependent on mechanical ventilation systems for the delivery of fresh air. At the same time, the use of building furnishings made from synthetic chemicals has increased, as has the recognition of microbiological organisms as potential exposure hazards. The sum result of these factors has been a steady increase in the frequency of indoor air quality complaints.
Analytical recommends a common sense approach to indoor air quality investigations. The approach of identifying potential sources of irritation and discomfort, rather than of testing the indoor environment for multiple contaminants, has become the industry standard. This is reflected in the growing body of regulatory requirements and guidelines, as described below:
Analytical has consistently endeavored to maintain its approach to the assessment and control of indoor air pollution problems on the leading edge of technology. We have performed hundreds of indoor air quality investigations, and utilize data-loggers and trained professional industrial hygienists. Our personnel possess a comprehensive range of technical skills for the identification of health hazards in working environments, and are accustomed to providing timely response and expedient solutions to air quality challenges.
A routine program of building inspection and assessment can identify problems before complaints and building-related symptoms occur. The cost of a proactive approach is usually much smaller than the cost of lost time, reduced productivity, and increased medical treatment which may arise when the effects of sick building syndrome have become established.
B. Technical Approach
Indoor air quality has become a major issue due to recent conservation efforts to reduce the cost of heating and cooling buildings, increased reliance on mechanical ventilation equipment, and growing awareness that air quality problems can impact the health, comfort, and productivity of building occupants. Since 1974, in the wake of the first oil embargo, the need to reduce building maintenance and operation costs has been a priority of building managers. To reduce these costs, new buildings have been constructed as hermetically sealed structures. Additionally, older buildings have been sealed by the addition of energy-efficient window and door closures. As a result, fresh air ventilation is provided primarily by way of mechanical air-handling equipment.
The energy savings have frequently been realized at the cost of reduced air quality. Inadequate fresh air ventilation has caused the products of human respiration, chemical off-gassing and biological contamination in buildings to accumulate. Some of the chemical species include carbon monoxide, various volatile organics, and formaldehyde. Often, the impact of chemical concentration increase is exacerbated by temperature effects, especially when temperature control is unable to maintain thermal parameters within the thermal comfort ranges established by ASHRAE Standard 55-1981.
Air quality complaints frequently are generated by inadequate ventilation, which is a commonly encountered condition. Renovation projects over the years may have dramatically altered air flow characteristics of the spaces, and ductwork may have been substantially modified. Maintenance schedules of the heating, ventilation and air conditioning (HV/AC) units may have been irregular, affecting the design performance of the units. Finally, casual housekeeping of the air handlers may have resulted in conditions conducive to microbiological contamination. All of these elements can have a significant impact on the quality of indoor air.
In many ways, the evaluation of indoor air quality complaints becomes a Sherlock Holmes style investigation into esoteric clues and vague physical symptoms. Often the complaints involve issues that have nothing to do with air quality. The investigator must learn to decifer the evidence and glean the kernel of truth from data that often sounds like this:
I was sick, sick unto death.
The walls of my cubicle closed in around me, and my skin crawled.
My eyes were seared by the emissions of light, and my head was pounding.
I gasped for breath, but the air had grown thin and unreliable. I was drowning.
I could not stop the swarms of ethereal invaders from teaming out of the ducts,
and the invisible hoard covered every inch of my body.
I choked as the awful chemistry of destruction entered my lungs.
I was helpless in their presence.
It takes a seasoned pro to make sense of these stories, and to determine if an irregularity in the building or its operation is at play. Read on to learn how an experienced hand gathers clues.
1. Investigation
A thorough walk through inspection of each floor is conducted to investigate and determine potential sources of IAQ contamination. The mechanical room air handling systems are visually inspected for microbiological contamination on the cooling and heating coils, drip pans and other system components. The maintenance records also are reviewed for each facility. Experienced field technicians qualitatively review the delivery capacities of the air handling systems to determine if air flow appears sufficient for the size and type building under investigation.
At locations and frequencies sufficient to characterize conditions and trends, comfort parameter (CO, CO2, temperature, relative humidity) readings are collected. We endeavor to collect comfort parameter samples at a rate of one sample for every 5,000 square feet of office space.
Upon completion of our visual investigation, the associated ventilation assessment/ventilation measurements (if required), measurement of comfort parameters, microbiological testing (if required), and analytical testing for volatile chemical compounds (if required), a report is generated. This report includes an assessment of our findings, the analytical data, and our recommendations and conclusions.
2. Temperature and Relative Humidity
Low humidity can cause eye, nose and throat irritation (particularly in the winter). High humidity encourages the growth of biological contaminants. The recommended range for humidity is 30% to 60%. ASHRAE recommends that temperature be maintained at 69° - 75° F in the winter and 73° - 79° F in the summer, with a relative humidity range of 30-60%.
All Analytical indoor air quality investigations include this parameter in an air quality investigation. Temperature and relative humidity are measured utilizing wet bulb/dry bulb mercury thermometers set in a Bacharach Sling Psychrometer. Data-logged measurements of temperature and relative humidity are collected with the TSI Q-Trak Portable Monitor, equipped with digital thermocouple sensors.
3. Carbon Dioxide
Carbon dioxide (CO2) is not normally considered a toxic air contaminant. Monitoring its concentrations (in conjunction with fresh air delivery measurements) gives an indication of the effectiveness of the air-handling system to supply and distribute fresh air throughout the work area. CO2 is a normal gaseous product of human respiration, and elevated levels can cause a "stale air" feeling, although no acute effects or health hazards exist.
National Institute of Occupational and Health (OSHA) guidelines call for sufficient fresh air to maintain CO2 concentrations below 2,500 ppm. More recent indoor air quality data indicate that in order to prevent employee discomfort, CO2 concentrations should not exceed 1,000 ppm.
Our experience has shown that many employee discomfort complaints have been registered when CO2 levels are measured at concentrations below 1,000 ppm. While the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) recommends that CO2 levels be maintained below 1,000 ppm in occupied buildings, we employ a more comparative approach. We generally are satisfied with the rate of fresh air exchange when CO2 remains below 700 ppm, and look for evidence of fresh air inadequacy when levels exceed 700 ppm. When CO2 concentrations exceed 1200 ppm, we generally are confident that fresh air delivery needs to be improved.
All Analytical indoor air quality investigations include analysis of CO2 as parameter in an air quality investigation. Carbon dioxide concentrations are measured utilizing the TSI Q-Trak Portable Monitor equipped with a non-dispersive infrared analyzer and datalogger.
4. Carbon Monoxide
Carbon monoxide (CO) is classified as a chemical asphyxiant, in that it has a higher affinity for blood hemoglobin than oxygen. This higher affinity, in the presence of elevated ambient air CO levels, results in an interruption of the normal supply of oxygen to body tissues. CO is one of the most prevalent indoor air pollutants. This gas can be introduced from the outdoor air from auto exhaust and industrial combustion. Additionally, other sources such as tobacco smoke and improperly vented combustion (stoves, hot water heaters), can produce sufficient CO concentrations in an indoor environment.
The Occupational Safety and Health Administration (OSHA) has established a permissible exposure limit (PEL) of 35 parts of CO per million parts of air for an 8-hour industrial exposure. At this level of exposure, most people will not experience any adverse health effects.
The PEL was developed for industrial exposure where health and safety factors are of primary concern. With indoor office environments, the industrial hygiene profession generally agrees that the OSHA PEL's are too high to be considered for limits. The outdoor ambient air quality standards established by the U.S. Environmental Protection Agency (US EPA) are more appropriate for the indoor environment. The EPA ambient air-quality standard for CO is 9 parts per million (ppm). In general, any CO reading above the background level of 1 ppm suggests that products of combustion may have entered the occupied building space.
All Analytical indoor air quality investigations include analysis of CO2 as parameter in an air quality investigation. Carbon monoxide concentrations are measured with the TSI Q-Trak Portable Monitor equipped with a chemical detector and datalogger.
5. Ventilation
Symptoms associated with poor indoor air quality include headaches, eye irritation, runny noses, sore throat, malaise, skin rash and shortness of breath. This symptom complex may have its etiological roots in a number of causes. One of these causes can be poor ventilation. Ventilation measurements are, therefore, often conducted to determine the amount of fresh air delivered to each occupant of the building. Both supply and return air volumes are measured. When performing these evaluations, Analytical references the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) recommendations. This society has recommended supplying fresh air at a minimum rate of 20 cubic feet per minute (cfm) per building occupant for the normal office building.
Analytical indoor air quality investigations utilize this parameter in extensive indoor air quality investigations in situations where symptoms have occurred over an extended period of time, and in which symptoms either occur throughout the building or in localized ventilated areas.
In order to determine the amount of fresh air being supplied to each occupant, and to determine if this amount is sufficient fresh air delivery, three separate and distinct environmental measurements are required:
Analytical indoor air quality investigations often utilize this parameter subsequent to the initial investigation, after ventilation delivery deficiencies have been discovered by the IAQ technician, to accurately measure and document quantities of air delivered to the work-place.
6. Volatile Organic Compounds
Volatile organic compounds (VOC’s) vaporize at room temperature and pressure. They are found in many indoor sources, including many common cleaning products and building materials. VOC’s can cause eye, nose, and throat irritation, headaches, loss of coordination, nausea, and possible damage to the central nervous system. NIOSH has established guidelines for total VOC levels in indoor environments. Total VOC air samples are collected in accordance with NIOSH Method 1500/1501, using charcoal sorbent tubes that are analyzed by gas chromatography with flame ionization detection. Results are reported as total hydrocarbon load calculated as benzene. If specific chemicals are known to be utilized with-in the building, testing of their individual concentrations, rather than a determination of total VOC concentrations, may be possible.
Analytical indoor air quality investigations utilize this parameter in extensive indoor air quality investigations in which volatile chemicals emission sources are identified. Often this testing is performed subsequent to the initial investigation.
7. Microbiological Testing
Persistent or intermittent water and excessive humidity breeds microbiological contamination. Bioaerosols are airborne particles such as molds, bacteria, and yeast that can be released from living organisms. HVAC systems with moist, warm conditions, enhanced by the presence of dust and dirt, make great homes for microorganisms. Moisture associated with condensation at HVAC chiller coils, roof or pipe leaks, or condensation from high humidity also provides excellent breeding areas for these microbes.
Hypersensitive reactions to mold and bacteria may ensue when microbial populations become amplified. Certain types of microorganisms, such as Legionella pneumonitis and Stachybotrys atrum, have been identified as specific causes of indoor air quality problems, and an identification of specific microbial genus and species can often provide useful information. Analytical indoor air quality investigations utilize this parameter in extensive indoor air quality investigations in which moisture damage and occupant symptoms indicate that microbiological agents are a possible cause of the indoor air quality problem.
Air sampling for the microbiological agents of fungi and bacteria is conducted with a Biotest Centrifugal Sampler, Model RCS Standard. The sampler directs air by centrifugal force onto strips containing agar nutrient media. A measured volume of air, generally 80 liters, is drawn past the strips, and the fungal and bacterial particulates adhere to the agar. The nutrient strips are sealed and returned to the laboratory, where they are cultured and incubated. Viable microbial colonies are enumerated by direct visual microscopic examination of the selective agar media. The airborne concentrations of bacteria and fungi are reported separately in units of colony-forming units per cubic meter of air (cfu/m3).