In striving for the construction of energy-efficient and cost-effective buildings, the imperative issue of the building's indoor air quality (IAQ) often is overlooked. This can lead to an unhealthy indoor environment and even to conditions such as sick building syndrome (SBS) or other building-related illnesses.
Poor IAQ is a major concern to businesses, building managers, tenants and employees because it can impact the health, comfort, well-being and productivity of the building occupants. This is especially important in industries where people spend a lot of time indoors. Many office workers, for example, will spend their entire working day inside a building. Healthy, comfortable employees invariably are more satisfied and productive.
While the measurement and monitoring of hazardous gases is a critical issue in industrial and workplace safety, often it has been concerned with acute levels of airborne pollutants. Today, there also are mounting concerns about the effect of long-term exposure to low levels of pollutants and to airborne pollutants found in office buildings.
POOR INDOOR AIR
In the past few decades, energy conservation measures have led to airtight building construction that can create problems with IAQ. Frequently, the ventilation systems are set to minimize the amount of fresh air entering and circulating within the building. This restriction impacts indoor air, allowing a build up of air contaminants within the building that are not properly removed.
There are many factors that can lead to an unhealthy indoor air environment, including poor or inadequate ventilation and airborne and chemical pollutants, emissions from printers and photocopiers, high concentrations of total volatile organic compounds (TVOCs), formaldehyde off-gassing and pollution from external sources (e.g. fumes) are just a few of the potential IAQ issues faced by employees.
When a substantial proportion of the occupants of a building experience symptoms associated with acute discomfort that usually are relived upon leaving the premises, the culprit can be sick building syndrome. The mechanisms still are not fully understood, but poor indoor air quality is thought to be a major contributor to these problems.
Health effects from indoor air pollutants may be experienced soon after exposure. The immediate effects usually are short-term and treatable, including irritation of the eyes, skin, nose and throat; upper respiratory congestion; headaches; dizziness; and fatigue.
Long-term exposure to low levels of pollutants could affect the exposed individual's health in future years. The U.S. EPA/Office of Air and Radiation reports that exposure to some indoor air contaminants can be severely debilitating and can result in respiratory diseases, heart disease and cancer. Exposure to high levels of some pollutants, such as carbon monoxide, can result in immediate death.
MONITORING INDOOR AIR
Typical indoor air quality investigation and examination consists of taking single-point measurements of pollutant levels. This monitoring method is unreliable, as the pollutant levels is subject to hourly, daily and even seasonal fluctuations. Building service professionals and designers alike have regarded these IAQ examination methods as being inadequate, considering today's environmental challenges.
A wireless monitoring system can ensure that almost any type of building is safe from the effects of poor IAQ. Continuous monitoring means the problems associated with single-point measurements are eliminated. The advances in technology have made it possible for a wireless system to control and monitor IAQ parameters continuously in real time. This has created a scientific approach to the systematic monitoring and management of any indoor air environment.
State-of-the-art gas sensors, automatic sampling, data logging, digital technology and IT have made it possible for IAQ profiling to be accurate and efficient and, therefore, a cost-effective system.
A wireless system enables simple, continuous detection and measurement of many of the factors that contribute to a building's indoor air environment, such as temperature, humidity and a number of toxic gases and compounds including carbon dioxide, carbon monoxide, nitrogen dioxide, sulphur dioxide, ozone, ammonia, formaldehyde and total volatile organic compounds (TVOCs).
The American Conference of Governmental Industrial Hygienists (ACGIH) publishes threshold limit values (TLVs) for these substances, which are defined as an exposure limit “to which it is believed nearly all workers can be exposed day after day for a working lifetime without ill effect.” The list of TLVs includes more than 700 chemical substances and physical agents, as well as dozens of biological exposure indices for select chemicals. Substances are nominated by the TLV committee of ACGIH based on new occupational exposure data or requests of government organizations, workers, industry, etc.
The limits are averaged over a specified period of time referred to as a time-weighted average (TWA). Two time periods are used — long term (8 hours) and short term (15 minutes). Short-term exposure limits (STELs) are set to help prevent effects such as eye, nose and throat irritations; headaches; dizziness; and fatigue. These symptoms can occur following exposure for a few minutes.
TLVs are recommendations. OSHA defines the regulatory limits. The agency includes permissible exposure limits (PELs) in some of the standards it publishes. PELs are regulatory limits on the amount or concentration of a substance in the air, and they are enforceable.
The National Institute for Occupational Safety and Health (NIOSH) has the statutory responsibility for recommending exposure levels that are protective to workers. NIOSH has identified recommended exposure limits (RELs) for around 700 hazardous substances. These limits have no legal force. NIOSH recommends their limits via criteria documents to OSHA and other occupational exposure limit-setting institutions.
HOW DETECTION WORKS
Should levels of a hazardous substance exceed the TWA and STEL limits for a specific parameter, the software found in the system gives an immediate warning. The system also can initiate immediate audible or visible warning of the presence of harmful gases in the air, thus protecting employees and the public. Buildings immediately can be evacuated, allowing for minimal exposure to the building occupants.
The alarm can be used to give a warning that gas concentration level has reached a non-critical but concerning level. It then can trigger the air conditioning system to respond before the gas concentration reaches a critical level. A further alarm can give a more severe warning when the gas concentration reaches a critical level.
Depending on your requirements, a wireless gas detection system has many advantages over conventional detection techniques. First, there are reduced installation costs, since a wireless system means there is no need for expensive cables and underground cable conduits. The entire system can be configured and operational in less than a day.
A wireless IAQ sensor network has the ability for detailed monitoring in inaccessible locations where a wired infrastructure is not viable or possible. A building-wide network of monitoring units can be achieved; this means a more detailed representation of indoor air quality in general. It is simple to expand the network by adding dedicated repeater nodes or additional wireless units, each unit with unique sensor specifications if necessary.
The wireless system can integrate with the building automation system. Dedicated software allows an entire wireless system to be managed and controlled from a single PC. The software can set parameters for temperature, humidity and concentrations of various gases, which then can activate and control the air conditioning and ventilation systems. It also can turn heating on and off and, as a last resort, trigger building alarms.
The collected data is presented on the controller PC in real time. The graphical display enables the user to identify trends and patterns in the sampling, while simple user interfaces enable ease of use and operation of the software. The user can monitor and control each individual unit and sensor using the software. Limits can be set on each parameter, which when exceeded will set off an on-screen alarm. Relays also can be installed, which can give visual and/or audible warnings if the limit is exceeded. The user also can create monitoring schedules using the software. This is ideal if monitoring only needs to take place for a set period of time, for example, during work hours only.
Continuous monitoring of IAQ enables a profile of the Indoor Air Environment to be created. Analysis of the recorded data through dedicated software allows for more efficient management of resources and energy. The software can be used as an analytical tool, in which trends can be identified and problem areas rectified. This should lead to better indoor air environments and safer, more comfortable working conditions.
If the building service engineer has the correct data relating to the day-to-day operation of the air conditioning system, improvements to the design and management of the ventilation system can be made. A more effective air-conditioning or ventilating system also has a positive impact on the environment. It ensures optimum human comfort, energy conservation, cost effectiveness and health and well-being for those inside the building.
Gareth Wyn Evans works for PPM Technology Ltd., which has developed technology that enables simple, effective and flexible management of indoor air quality, offering facility managers and health and safety personnel with the data they need for the effective management of air quality within a building.