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All air samples were collected using an Aircuity IAQ100 IAQ Evaluation System. This self-contained device draws in ambient room air at a predetermined rate. The air follows a path past several sensors and is exhausted away from the inlet port.
Integrated circuit sensor with a range of 34°F-120°F (1°C-49°C), accuracy of +-1°F, resolution of 0.1°F, and immediate response time.
Indoor environmental issues involving thermal discomfort are the most common and the most easily addressed. Many complaints can be minimized by maintaining the conditions recommended by ASHRAE: winter temperature of between 68° and 75°, and summer temperature of between 73° and 79°F. This evaluation system uses an even more stringent range of 71 to 74 for a typical/comfort setting based upon case studies and practical experience. Relative humidity is closely related to temperature and should also be taken into account when evaluating thermal discomfort. See Relative Humidity.
An non-dispersive infrared sensor with a range of 0-3000 ppm, accuracy of +-50 ppm, resolution of 5ppm, and response time of 2 minutes.
People exhale CO2 as a normal byproduct of metabolism. Although the indoor concentrations of CO2 resulting from usual occupant activities are rarely hazardous, this gas can serve as a good indicator of room ventilation rate. This is because CO2 concentrations in indoor air increase in inverse proportion to the amounts of outdoor air that are supplied to a room, that is, the more outdoor air supplied to a room, the lower the CO2 concentration. Supplying adequate ventilation is also important for diluting airborne concentrations of indoor contaminants that may build up due to materials in the space or to occupant activities. By monitoring CO2 levels in an occupied room or area and assuming that an equilibrium has been reached, it is possible to estimate the amount of outdoor air that is being supplied to an area.
ASHRAE, a professional organization dedicated to promulgating standards for industry based on a rigorous peer review process, has adopted standards that specify minimum supply quantities of outdoor air for occupied building spaces. While these standards do not have force of law, they are cited widely and are generally regarded as state-of-the-art. These standards, including the IAQ standard, are reviewed every five years so that they incorporate the latest scientific developments and findings.
ASHRAE regards an outdoor air supply rate of 20 cfm (cubic feet per minute) per person as a satisfactory comfort criterion for many indoor environments, such as offices, conference rooms, and shops (ASHRAE 62-1999). A formula contained in this ASHRAE document provides for the conversion of an indoor CO2 measurement to a cfm per person value. Using this calculation, a ventilation rate of 20 cfm per person corresponds to CO2 concentrations less than 850 parts per million (ppm) during occupied hours, using the ASHRAE assumptions of a specific activity level for office workers, an outdoor air concentration of 300 ppm CO2, and steady-state operating conditions.
Capacitance with integrated circuit sensor with a range of 5-100%, accuracy of +-2%, resolution of 15, and immediate response time .
Humidity levels of between 20% and 60% are generally considered to be desirable in indoor environments. At levels below 20% people tend to complain of dry-stuffy air, and levels greater than 60% can foster the growth of harmful microbials and molds. Because the capacity of air to hold water decreases with temperature, relative humidity reflects the percentage of water the air can hold at any given temperature. Condensation appears on cool surfaces when the air in close proximity is in turn cooled to below its dew point.
In northern climates, the relative humidity can fall to levels well below 30% during the heating season. While this may be slightly uncomfortable for occupants, humidification of the air can potentially cause more problems through condensation. This situation is taken into account in the recommendations given by IAQ Advisor.
Metal oxide sensor with a range of 0-2000 ppb, accuracy of +-15 ppb, resolution of +-12 ppb, and response time of 2 minutes.
Ozone is a common outdoor pollutant in urban areas. Ozone is formed in the troposphere by atmospheric reactions between nitrogen dioxides, hydrocarbons, oxygen, and sunlight. Ozone gas ( O3 ) is a colorless gas with a distinctive "electric" odor and metallic taste. It is an unstable and highly reactive molecule that quickly breaks down to oxygen ( O2 ).
Indoors, common sources of ozone include photocopying machines and laser printers. O3 is emitted in detectable levels by almost all photocopiers and laser printers as a by-product of the electrophotographic process. The gas source is the corona wire producing an electrical discharge that makes the toner powder temporarily adhere to the print drum just before the paper passes over the drum. Therefore, ozone is only produced when the machine is printing, not when the unit is in stand-by mode.
The health effects associated with ozone are mostly acute and are related to irritation of the respiratory system. Symptoms associated with exposure include upper respiratory irritation, cough, dyspnea, and chest pain. Temporary changes in lung function have been associated with exposure to 0.2-0.4 ppm of ozone. Exposures to significantly higher concentrations can cause permanent lung damage, such as pulmonary edema and hemorrhage. (Proctor et. al. 1991) Several federal agencies have established health standards or recommendations to limit human exposure to ozone.
The Occupational Safety and Health Administration (OSHA) requires that workers not be exposed to an average concentration of more than 0.10 ppm for 8 hours. The National Institute of Occupational Safety and Health (NIOSH) recommends an upper limit of 0.10 ppm, not to be exceeded at any time. Additionally, the American Conference of Governmental Industrial Hygienists (ACGIH) has recommended that 15-minute short-term exposures to ozone not exceed 0.3 ppm. Both these recommendations are used to evaluate ozone data in the Aircuity system.
Metal oxide sensors with a range of 0-125 ppm, accuracy of +-25%, resolution of +-10%, and response time of 1 minute.
Volative Organic Compounds (VOCs) include a large number of compounds commonly found in indoor and outdoor environments. These compounds have many sources, such as evaporation of isopropyl alcohol, gasoline, paint solvents, spray product propellants, combustion by-products, emissions from household furnishings, and some natural sources. Because we manufacture, use, and dispose of products containing VOCs, many of these compounds are ubiquitous in the air we breathe.
Health effects from exposure to this group of compounds at typical indoor and outdoor concentrations are not generally considered to be problematic. It is known that exposure to certain specific VOCs at concentrations greater than 1,000 times the typical indoor/outdoor levels may cause adverse health effects.
Measurement of total VOCs (TVOCs) is an integrated measurement of the concentrations of all VOCs in an air sample. TVOC measurements in indoor environments are taken primarily for two reasons. The first is to detect any abnormally high levels of VOCs that would indicate the need for more detailed investigations for specific compounds. The second is to obtain readings from different areas and, by comparing the results from these areas, determine potential sites or sources of VOCs, such as methane gas, gasoline vapors, exhaust gases, or vaporized solvents.
Due to differences between readings obtained using different detector designs, as well as the concentration response variations between VOCs on each, the term "index" is used rather than ppm to describe the TVOC concentration. Even though each sensor is calibrated to the same concentration of a particular VOC, a concern is that by expressing the concentration in parts per million confusion may result when comparing these readings to those obtained by other devices, potentially in the same building.
No recommended guidelines for airborne concentrations of TVOCs currently exist. Measurements of TVOCs are, however, useful for identifying potential sources or locations of VOCs that could present health or fire hazards for humans. This data can also be used to determine the cause and effect of various processes that may be associated with the release of these compounds.
A laser light scatter sensor with a range of 0.3-10 microns.
Particles in indoor air, collectively referred to as dust, form a complex mixture that originates from a variety of sources, including the outdoors, office equipment, building materials, furnishings, and occupants. Particles are an important category of indoor air pollutants because in high enough concentrations, they can act as irritants to the eyes, skin, and respiratory tract.
Particle size affects how far particles can penetrate into the respiratory tract and determines the sites of possible health effects. Inhalable particles are those that can deposit anywhere in the respiratory tract from the nose and upper airways to the lower airways and lung tissue where gas exchange occurs. The diameter of inhaled particles that can reach the nose, mouth, trachea, and airways in the lungs but not in the gas exchange areas is generally between 10 microns (mm) and 100 mm in aerodynamic diameter (1 micron equals approximately 1/25,000 of an inch). Particles less than 5 mm can reach the trachea and all of the airways. Respirable suspended particles (RSP), that is, those that can initially reach the gas exchange region of the lungs, are defined as particles in the air that are less than 3.5 mm in aerodynamic diameter. Because RSP are small enough to reach deeply into the lungs, they may present long-term health concerns. Environmental tobacco smoke is one example of a major source of RSP..
The EPA's 24-hour standard for PM10 is 150 micrograms per cubic meter (µg/m3), (0.150 milligrams per cubic meter [mg/m3]), and cannot be exceeded more than once per year; the standard for the year is an average of 50 µg/m3 (0.050 mg/m3). The Occupational Safety and Health Administration (OSHA) has promulgated an occupational permissible exposure limit (PEL) for "particulates not otherwise regulated" of 15 mg/m3 (15,000 µg/m3) for total dust and 5 mg/m3 (5,000 µg/m3) for the respirable fraction of these particulates for eight-hour time-weighted average (TWA) exposures.
Because most of the above guidelines deal with outdoor particle levels, Aircuity has chosen to set limits of 20 and 40 µg/m3 respectively for the PM2.5 and PM10 levels in commercial office buildings. These values were arrived at by reviewing particle data collected in approximately 100 commercial office buildings.
The IAQ100 utilizes a particle counter to measure and record both short and long term trends within the building. However, the only standards developed for IAQ have used a mass measurement system, in which particles of these size ranges are captured on a filter during a specified time period and weighed. In order to give a rough comparison between the particle count information collected by the portable monitor and the current standards, a conversion is used that is based upon the NIST standard material "Arizona Road Dust", and assuming a log normal distribution of particles within the two size categories. This conversion is commonly employed in most commercially available particle counting equipment. The portable monitor and database therefore track and record particle count information, and a conversion to mass is performed during the reporting process for comparative purposes
Integrated circuit sensor with unlimited range, accuracy of 0.2 pCi/l, resolution of 0.2 pCi/l, and response time of 1 hour.
Radon is a colorless, odorless, radioactive gas that occurs naturally and is found throughout the environment at very low levels. The most common source of indoor radon is uranium in the soil or rock on which buildings are built. As uranium naturally breaks down through radioactive decay it forms radium that in turn decays to radon which is a gas. Radon then enters buildings through dirt floors, cracks in concrete walls and floors, floor drains, and sumps. Radon becomes a health concern when it becomes trapped in buildings and when concentrations build up in indoor air. Inhaled radon (which is radioactive) then breaks down further into decay products (also called radon daughters or progeny). These progeny emit alpha particles that can damage cells lining the airways and possibly lead to cancer.
The only known health effect associated with exposures to elevated levels of radon is lung cancer. EPA estimates that about 5,000 to 20,000 lung cancer deaths a year may be attributed to radon in the United States.
The action level for radon in air in residences established by the EPA is 4.0 picocuries/liter (pCi/L). It is based upon an exposure of 18 hours per day for 40 years. No standards or guidelines currently exist for occupational exposures in commercial office settings, although several residential radon standards and guidelines have been established by various public health and professional organizations. The most stringent residential standard is the Swedish standard of 2 pCi/L.
An electrochemical sensor with a range of 0-150 ppm, accuracy of +-3 ppm, resolution of 2 ppm, and response time of 1 minute.
CO is a colorless, odorless, and tasteless gas produced by incomplete combustion of carbon fuels. It is a common component of exhaust from motor vehicles and heating units, such as boilers and space heaters, and also is present in tobacco smoke. Although the airborne concentrations of this gas in most indoor environments are usually low, elevated levels can occur under certain situations, such as entrainment of exhaust from trucks idling at a loading dock into a building air intake, migration of air from traffic or parking garages, or leakage of boiler flue gases into a building.
Inhaled CO readily binds to hemoglobin in red blood cells and results in decreased delivery of oxygen to tissues (Coultas and Lambert 1991). The extent of symptoms produced by CO inhalation depends on both personal activity level and airborne concentrations. Exposures to high concentrations may produce headaches, dizziness, fatigue, and nausea. Although average indoor concentrations of CO are usually less than 2 ppm, levels can reach 5 ppm to 10 ppm inside motor vehicles. Symptoms become clinically apparent when the amount of CO bound to red blood cells, termed carboxyhemoglobin, reaches approximately 10%. As an example, a person at rest would have to inhale 80 ppm of CO for eight hours to reach this 10% carboxyhemoglobin level.
The U.S. Environmental Protection Agency's (EPA) National Ambient Air Quality Standard (NAAQS) for CO is 35 ppm for a one-hour exposure and 9 ppm for an eight-hour exposure (EPA 40CFR50.8). Based on this EPA standard, ASHRAE established an IAQ standard of 9 ppm of CO for an eight-hour exposure (ASHRAE 62-1999).