The importance of indoor air quality (IAQ) monitoring
In striving to construct energy-efficient, cost-effective buildings, the imperative issue of their indoor air quality (IAQ) is often overlooked. This can lead to an unhealthy indoor environment and to conditions such as sick building syndrome (SBS) or other building related illnesses (BRI).
A wireless monitoring system can ensure almost any building type is safe from the effects of poor IAQ. This is a major concern to businesses, building managers, tenants, and employees because it can impact occupant health, comfort, well being, and productivity. This is especially important in industries where people spend a lot of time indoors (e.g. office workers who spend entire working days inside). Healthy, comfortable employees are invariably more satisfied and productive.
Measuring and monitoring hazardous gases is a critical issue in industrial and workplace safety. Conventionally, worker safety has been concerned with acute levels of airborne pollutants; today there is also mounting concern about the affect of long-term exposure to low levels of these.
Gradually, building designers are realizing the importance of IAQ in the workplace and are taking this into account when designing modern buildings and air conditioning systems.
Placing an IAQ monitoring system in new buildings and facilities enables immediate identification of IAQ problems, the sources and causes of any IAQ problems can be eliminated before the facility is operational and before complaints are made.
There are many factors that can lead to an unhealthy indoor air environment, including:
● poor or inadequate ventilation;
● airborne and chemical pollutants;
● ozone (O3) emissions from printers and photocopiers;
● high concentrations of Total Volatile Organic Compounds (TVOCs);
● formaldehyde (CH2O); and
● pollution from external sources (e.g. fumes).
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 facility. This restriction impacts indoor air, allowing a buildup of air contaminants within the structure that are not properly removed.
Sick building syndrome is said to occur when many building occupants experience symptoms associated with acute discomfort that are usually relieved when leaving the premises. The mechanisms are still not fully understood, but poor IAQ is thought to contribute greatly to this problem.
Health effects from indoor air pollutants may be experienced soon after exposure. The immediate ones are usually short-term and treatable, including:
● eyes, skin, nose, and throat irritation;
● upper respiratory congestion;
● dizziness; and
Long-term exposure to low pollutant levels could have an affect on an individual’s health in future years. According to the U.S. Environmental Protection Agency (EPA)/Office of Air and Radiation (OAR), these can be severely debilitating or become fatal illnesses, including some respiratory diseases, heart disease, and cancer. Exposure to high pollutant levels—such as carbon monoxide (CO)—can even result in immediate death.
Typical IAQ investigation and examination consists of taking single-point measurements of pollutant levels. This monitoring method is unreliable, as the pollutant levels are subject to hourly, daily, and seasonal fluctuations. Building service professionals and designers alike have regarded these IAQ examination methods as being inadequate considering today’s environmental challenges.
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 information technology (IT), have made it possible for IAQ profiling to be an accurate, efficient, and cost-effective system.
PPM Technology has used this technology in developing the Wireless IAQ Profile Monitor that enables simple, effective, and flexible management of air quality. It is able to collect a complete and accurate record of IAQ, presenting facility managers and health and safety officers with the data they need for effective air quality management within the building.
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 numerous toxic gases and compounds, including:
● carbon dioxide (CO2);
● carbon monoxide (CO);
● nitrogen dioxide (NO2);
● sulphur dioxide (SO2);
● ozone (O3);
● ammonia (NH3);
● methanol (CH20); and
● total volatile organic compounds (TVOC).
Controlling these IAQ parameters would improve occupant comfort and work efficiency as well as immediate and long-term health.
Permissible exposure limits
These substances are among the hundreds under the regulation of occupational exposure limits (OEL). These are limits to control exposure to dangerous substances in the workplace. This is achieved by setting the maximum amount of (air) concentration of a specific substance.
The limits intend to protect workers from excessive exposure to toxic substances. They are averaged over a specified period of time referred to as a time-weighted average (TWA). Two time periods are used—long term (eight 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.
Should levels of hazardous substance exceed the TWA and STEL limits for a specific parameter, the software will give an immediate warning of this. The system can also initiate immediate audible and/or visible warning of the presence of harmful gases in the air, thus protecting employees and the public. Buildings can be immediately evacuated giving minimal exposure to the building occupants.
The alarm can be used to give a warning that the gas concentration level has reached a non-critical but concerning level. It can then trigger the air-conditioning system in response before the gas reaches a critical level. A further alarm can give a more severe warning when this occurs.
As a result, the health of the workers and members of the public are safeguarded. The affected areas will not be contaminated for as long, thus minimizing interruptions to the working day and, consequently, improving productivity.
A wireless gas detection system has many advantages over conventional detection techniques. First, there is reduced installation costs—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 also 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 IAQ in general. A network can be extended simply by adding dedicated repeater nodes or additional wireless units—each unit with unique sensor specifications if necessary.
A large number of units can be linked using this mesh networking; the system can show precise changes in concentration of selected IAQ parameters in various locations over time. The data can be received via the PC module, which is then stored and can be used as detailed statistical data using the dedicated software. The software can also produce reports and configure individual alarms for particular sensors.
The wireless system can integrate with the building automation system as 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 hazardous gases, which can then activate and control the air-conditioning and ventilation systems. It can also turn heating on and off, and as a last resort trigger building alarms.
The fact that the monitoring system can connect and control 3rd party systems such as Air-Conditioning units can help ensure that buildings meet ASHRAE Standard 62.1 "Ventilation for Acceptable Indoor Air Quality"
This standard defines requirements for ventilation and air-cleaning system design, installation, commissioning, and operation and maintenance. Ventilation requirements of this standard are based on chemical, physical, and biological contaminants that can affect air quality. This standard contains requirements, in addition to ventilation, related to certain sources, including outdoor air, construction processes, moisture, and biological growth.
A more effective air-conditioning or ventilating system would also have a positive impact on the environment. It would take care of human comfort, energy conservation, cost effectiveness and health of the occupants inside the building. In order to ensure the preset targets of air quality are met but not over or under provided, signals from real time monitoring to control the air conditioning and ventilation systems could be used. It can help avoid wastage of energy and resources due to better control of the air conditioning system.
In order to dilute the indoor air pollutants a good ventilation system must be in place. An over-ventilated air conditioned building is not energy efficient.
It is a difficult balance to save money and energy yet maintain a comfortable and healthy environment. Therefore, the logical solution to controlling indoor air pollution is good ventilation coupled with IAQ monitoring using gas sensors.
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; simple user interfaces enable easy 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 can also be installed which can give visual and/or audible warnings if the limit is exceeded. The user can create monitoring schedules using the software, which is ideal if monitoring only needs to take place for a set period of time (e.g. during work hours only).
A recent trial setup of a wireless IAQ monitor system was held in Honk Kong; the data was collected at regular one-minute intervals using four IAQ monitor units for four consecutive days. The units were placed in various locations around the building for a wider analysis of the buildings indoor environment. The information gathered was automatically stored onto the controller PC that is connected to the wireless mesh system that had installed the software.
The results gathered from the test demonstrated that much could be done to save energy, thus reducing the building’s CO2 emissions. The power required to air-condition a 50-story office building—such as the one in which the test was conducted—can easily exceed 10 million kWh per annum. Equipping a building with an IAQ monitoring system can provide building service professionals and facility managers with the data they need for effective air quality management within the building.
Continuous monitoring of IAQ enables a profile of the indoor air environment to be created, and an analysis of the recorded data through dedicated software allows for more efficient resource and energy management. The software can be used as an analytical tool to identify trends and rectify problem areas—leading to a better indoor air environment and safer, more comfortable working conditions.
If the building service engineer has the correct data relating to the daily 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 and ensures optimum human comfort, energy conservation, cost effectiveness, and health and well-being of those inside the building.