It is a difficult balance to save energy and money yet maintain a comfortable and healthy indoor air environment. A logical solution to controlling indoor air pollution is good ventilation coupled with indoor air quality (IAQ) monitoring using gas sensors. This can ensure healthy indoor air as well as a more efficient HVAC system.

IAQ relates to a number of environmental factors inside a building that can impinge on the health, comfort, or work performance of the building’s occupants. Monitoring IAQ is vital because it is estimated that the average person spends 90 percent of their time breathing “indoor air.”

IAQ is a major concern to businesses, building managers, tenants, and employees because it can impact occupant health, comfort, well being, and productivity. The issue is especially important in situations where people spend a lot of time indoors (e.g., office workers who spend entire working days inside). Healthy, comfortable employees are more likely to be satisfied and productive.

Building designers, architects, and facilities managers are realizing the importance of IAQ and are taking this into account when designing and managing modern buildings and HVAC systems.

Sick Building Syndrome

Sick Building Syndrome (SBS) is said to occur when many building occupants experience symptoms associated with acute discomfort that are usually relieved when leaving the premises.

Often neglected by building service professionals up until the last century, many had never even considered a building’s carbon emission or carbon footprint. It was only recently that professionals and members of the public began to seriously consider the implications of IAQ that directly affects health and quality of life and the greater environment.

SBS typically occurs in large open-plan offices. There are many factors that can lead to an unhealthy indoor air environment, including:

• Poor or inadequate ventilation;

• Unsuitable temperature and humidity;

• 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., vehicle fumes coming into the building).

Green Buildings

In the past few decades, energy conservation measures have led to green buildings, which call for 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 because it allows a build-up of harmful pollutants and contaminants.

Although in many cases the issue of indoor air quality is addressed, the primary concern of green building is the overall impact the building and building process has on the environment. It does not have the health of the occupants as its priority. So, at times, this focus can be at the expense of indoor quality and ultimately the building occupant’s health.

Health Effects

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;

• Headaches;

• Dizziness; and

• Fatigue.

Long-term exposure to low levels of certain pollutants could have an effect 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 result in immediate death.

Continuous Monitoring

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

Continuous monitoring instruments for IAQ eliminate the problems associated with single-point measurements. Multiple IAQ parameters can be monitored continuously in real-time. This enables simple, effective, and flexible management of air quality. The instruments are able to collect a complete and accurate record of IAQ, presenting the data required for effective air quality management within the building.

These instruments can continuously detect and measure 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;

• Ammonia (NH3);

• TVOCs;

• Methane;

• Formaldehyde; and

• Glutaraldehyde.

The instrument’s software can set standards for temperature, humidity, and for concentrations of hazardous gases. When the pre-set standards are exceeded or underachieved, it can 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.

Collected data is presented on the controller PC/laptop in real-time. Graphical display enables the user to identify trends and patterns in the sampling.

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 building-wide network of monitoring units is possible — this means a more detailed representation of IAQ in general. A large number of units can be linked using wireless communication; the system can show precise changes in concentration of selected IAQ parameters in various locations over time.

HVAC System

Carbon dioxide is a good indicator of how efficient the ventilation system is within a building. The sensor results gathered for carbon dioxide coupled with temperature and humidity readings will give an indication of the effectiveness of the HVAC system in the building.

According to ASHRAE standards, carbon dioxide levels less than 800 ppm indicate that sufficient ventilation is being supplied to the building.

In order to dilute the indoor air pollutants, a good ventilation system must be in place. An over-ventilated building is not energy efficient. In order to ensure the preset targets of indoor air quality are met but not over- or under-provided, signals from real time monitoring to control the HVAC system can be used, helping avoid energy waste.

A recent trial setup of PPM Technology’s IAQ Monitor system was held in Hong 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 building’s indoor environment.

The results gathered from the test demonstrated that much could be done to save energy and reduce 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 year. 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, and help achieve a 10 to 20 percent saving in emissions, which will ultimately save money.


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 professional has the correct data relating to the daily operation of the HVAC system, improvements to the design and management of the ventilation system can be made. A more effective HVAC 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.

Publication date: 05/07/2012