Wireless Monitoring for a Safe Indoor Environment
In striving for the construction of energy
efficient and cost-effective buildings, the imperative issue of the buildings Indoor Air Quality (IAQ) is often overlooked. This can often lead to an unhealthy indoor
environment and even to conditions such as Sick Building Syndrome (SBS) or other Building Related Illesses (BRI).
A wireless monitoring system can ensure that almost any type of building is safe from the effects of poor Indoor Air Quality; 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 – for example, many office
workers will spend their entire working day inside a building. Healthy, comfortable employees are invariably more satisfied and productive.
Measurement and monitoring of 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 pollutants.
There are many factors that can lead to an unhealthy Indoor Air Environment including poor or inadequate ventilation, airborne and chemical pollutants, Ozone emissions from printers and photocopiers, High concentrations of Total Volatile Organic Compounds (TVOC's), Formaldehyde 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 minimise 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.
Sick building syndrome is said to occur when a substantial proportion of the occupants of a building experience symptoms associated with acute discomfort that are usually relived upon leaving the premises. The mechanisms are still 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 are usually 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 have an affect on an individuals health in future years, these, according to the U.S. EPA/Office of Air and Radiation, can be severely debilitating or fatal illnesses including some respiratory diseases, heart disease, and cancer. Exposure to high levels of some pollutants, such as carbon monoxide, can even result in immediate death.
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 indeed 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 IT, has made it possible for IAQ profiling to be a accurate, efficient and therefore a cost effective system.
PPM Technology have utilised this technology in developing the
Wireless IAQ Profile PPMonitor; it enables simple, effective and flexible management of Indoor 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 the effective management of air quality 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 a number of toxic gases and compounds including Carbon Dioxide, Carbon
Monoxide, Nitrogen Dioxide, Sulphur Dioxide, Ozone, Ammonia, Formaldehyde and Total Volatile Organic Compound’s (TVOC’s).
Controlling these IAQ parameters would improve the comfort and work efficiency of the occupants as well as their immediate and long- term health.
These substances are amongst 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. Limit values are laid down throughout the EU, but each Member State establishes its own national Occupational Exposure Limits. In the UK the Health and Safety Commission approved Workplace Exposure Limits (WEL) applies to all workplaces.
The limits intend to protect workers from excessive exposure to toxic substances, the exposure 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 irritations of the eye, nose and throat, headaches, dizziness and fatigue, these symptoms can occur following exposure for a few minutes.
Should the levels 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 gas concentration level has reached a non-critical but concerning level. It can then trigger the air conditioning system in response 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.
As a result the health of the workers/members of the public are
safeguarded. The affected areas will not be contaminated for as long, thus minimising interruptions to the working day and consequently improving productivity.
A wireless gas detection system has many advantages over conventional detection techniques. First of all 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 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. A network can be extended simply; by adding dedicated repeater nodes or additional wireless units, each unit with unique sensor specifications if necessary.
The PPMonitor utilises the
low-power, high-performance Zigbee mesh wireless network to communicate. A large number of units can be linked using the Zigbee wireless mesh networking; the system can show precise changes in concentration of selected IAQ parameters in various locations overtime. The data can be received via the PC Zigbee
IET
November/December 2010
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