Tag Archives: human health

Energy Efficiency and Indoor Air Quality

Some of the key factors for improving energy efficiency in relation to indoor applications are the control of Relative Humidity (RH) and temperature. The question is, how to control RH to acceptable levels in an energy efficient manner. Energy efficient humidity control has a very strong bearing on thermal comfort, Indoor Air Quality (IAQ) and eventually on the health and performance of occupants in air-conditioned buildings.

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Passivhaus buildings are built to a voluntary standard to improve energy efficiency and reduce ecological footprint.

IAQ control seeks to reduce Volatile Organic Compounds (VOCs), and other air impurities such as microbial contaminants. As such it is important to control relative humidity which can be a key factor leading to mould growth and the presence of bacteria and viruses, dust mites and other such organisms.

Buildings rely on a properly designed ventilation system to provide an adequate supply of cleaner air from outdoors or filtered and recirculated air

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Buildings may rely on dehumidifiers like the one above to reduce RH levels to a comfortable range

Air-conditioning systems typically employ a high level of air recirculation to save energy during cooling and dehumidification. Typically recirculation rates are around 80-90%, but can sometimes be even higher. The challenge is not so much in dehumidification, but in doing so without having to overcool. As such, ventilation is integrated for general comfort and economical saving.

Rooms are often designed with specific conditions in mind including temperature, humidity, brightness, noise, and air flow. Careful engineering and implementation of building automation and control is the only way to ensure energy efficiency and building operation conditions are met during occupancy, at the lowest possible costs.

IAQ Facts:

Energy Efficiency (EE) refers to either the reduction of energy inputs for a given service or the enhancement of a service for a given amount of energy inputs.

Relative humidity is highly temperature dependent, so if the temperature is stable, it is much easier to achieve a stable RH.

Air in our atmosphere is a mixture of gases with very large distances between molecules. Therefore, air can accommodate a large quantity of water vapor. The warmer the air, the more water vapor can be accommodated.

Why the need to measure, temperature and relative humidity?

Precise temperature control of air which is supplied to a room results in maximum comfort for the occupants. The temperature should be held constantly at a particular set point to achieve this comfort.

Readings from temperature transmitters installed in the air supply duct are compared to readings inside a particular room. It is easiest to achieve a constant room temperature if there is little difference between the two values. Air temperature control in supply ducts can be employed in rooms in which the air handling unit is used mainly for the renewal of air.

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Rotronic manufactures temperature and humidity transmitters such as the one above which are suitable for use in spaces where appearance is a factor.

It is with good RH control that we can process the air for air conditioned rooms independent of the state of outside air and the processes taking place in the room. This way the RH remains constant or within the preset limits and thus energy consumption for humidification and dehumidification is minimized.

Air conditioning is supposed to maintain room temperature and RH as precisely as possible through the use of systems which monitor and control temperature and humidity in the room (or in the air supply ducts to the room). Systems must be dynamic to manage the changing room air quality depending on the occupants and usage.

With precise measurement and control of temperature and humidity, energy consumption for humidification & dehumidification as well as heating and cooling can be reduced leading to energy efficient building operation with lower energy costs and healthier occupants.

Phil Robinson
Rotronic UK

CO2 in Garages and Tunnels.

Modern vehicle engines emit many harmful substances, including carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), hydrocarbons and some 20 other gases. It is known that all engines produce CO, particularly at cold start. To protect ourselves from this toxic gas, vehicles are installed with catalytic converters. This means that a warm running modern engine with converter generates 140 times more CO2 than CO.

catalytic_converterCatalytic converters convert a lot of the CO produced by an engine into CO2.

Facts and Figures

The longest tunnel in Switzerland will be the Gotthard Base Tunnel (under construction) that will be 57km long. The tunnel is a railway tunnel.

The longest car tunnel in the world is located in Norway, the Laerdal tunnel, 24km.

The LEP tunnel in Cern, Switzerland/France is a 26km circular ring.

Why the need to measure CO2?

Old vehicles (pre-catalyst) generate a lot of carbon monoxide pollution, to solve this, modern vehicles were installed with catalytic converters. Catalytic converters are not very efficient during cold start up but once warm they can convert CO to CO2 very effectively. This means modern engines emit much higher quantities of CO2 than CO. It is well-known that CO is extremely toxic but CO2 in high levels can also be hazardous to health. To ensure healthy air quality it is important to provide excellent ventilation in garages and tunnels, however running a ventilation system constantly is inefficient especially when few cars are running at a time.

SAM_3014Levels of CO2 in large indoor car parks can become extremely dangerous if not properly controlled.

In garages and tunnels vehicles can be operating in both warm and cold conditions, therefore it is important to measure both CO and CO2 to ensure a safe environment. Today there are laws around the measuring of CO – the maximum allowed value is 35 ppm. There are however, currently no rules on measuring CO2 but this is equally as important.

How does it work?

A meter can both control and alarm locally, as well as being part of a larger complete system. This application is similar, for example, to the ventilation requirements in a classroom.

The ventilation need depends on the number of cars running in a garage or tunnel instead of the number of students in a classroom. The sensors usually used to measure CO2 and CO in public garages and tunnels are capable of covering an area of around 250 m2.

Reduced Costs

A study was made in a garage containing 77 parking places and covering an area of 1,445 m2. The study showed that using sensors to control the ventilation reduced the fan operating time by 90% compared to constant running. The electricity cost was about €0.09 per kW/h (including energy tax and VAT) and the fan used 1.5 kW/h in operation. This meant that the demand-control solution produced an energy saving, per month, of 970 kW/h, and a resulting reduction in running-costs of ca 85.32 €/month. If all residential garages were equipped this way the sum of energy saved would make for a considerable benefit to society and the environment. A larger garage would have saved even more money thanks to the controlled ventilation system.

c700x420Ventilation plays a vital role in keeping in door parking spaces safe, especially when busy.

Another benefit is fewer people suffering from CO or CO2 poisoning being admitted to hospitals. As well as being good for the health of the general public, This helps reduce the costs of health care to the government.

Phil Robinson                                                                                                           Rotronic UK

CO2 and Indoor Air Quality (IAQ)

Indoor Air Quality in General

The quality of the air in a room can greatly affect the health, productivity, and well being of any occupants. Previously the temperature and humidity of indoor air were considered as the most important parameters contributing to air quality, but there are several other factors which must be taken into account.

Indoor Air Quality (IAQ) problems are very often caused by gases or particles released into the air by pollution sources. This can be avoided by carefully selecting the materials which are to be used inside dwellings, offices, classrooms, gymnasiums, hotels, shopping malls, hospitals and in all en-closed spaces which are inhabited. But there is another source of air pollution, which cannot be avoided. this other source is people themselves. Every time a person exhales, CO2 is released. Inadequate ventilation may increase CO2 concentration to an unhealthy or even life-threatening level.

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CO2: made up of 2 oxygen atoms, double bonded to a single carbon atom.

The most important control parameters for a good Indoor Air Quality are temperature, relative humidity and CO2 concentration. If these values are used with an intelligent air conditioning system, an energy efficient air supply can be used to produce a high quality atmosphere.

Facts & figures:

CO2 is a naturally occurring molecule consisting of two oxygen atoms and a single carbon atom.

At standard temperature and pressure CO2 is a gas, invisible and without any smell or taste.

CO2 is 50% heavier than air and has no liquid state under atmospheric pressure.

In the earth’s atmosphere CO2 has a concentration of 390 ppm by volume.

The worldwide industry produces approximately 36 billion tons of CO2 per year.

Industrial activities are responsible for an increase of atmospheric CO2 concentration and thus for an increase of global warming (greenhouse effect).

Influence of CO2 on Humans

Only a small amount of the atmosphere is made up of CO2, the prevailing components are nitrogen and oxygen. The natural outdoor atmosphere CO2 level is approx. 390 ppm. Increasing this concentration causes several symptoms of poisoning, ranging from drowsiness at around 1´000ppm to unconsciousness and even death at above 10´000 ppm. Even if a  rise in CO2 concentration has not yet severely influenced the health of people, it may reduce their productivity, efficiency and well-being.

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Some of the possible health effects

How to Measure CO2

The most common measuring method for CO2 concentration nowadays is based on a spectroscopic principle. Sending infrared light (IR) with a wave length of 4.23 μm through a gas sample. CO2 molecules in the sample absorb the light at this wavelength. an IR sensor is then used to detect any changes in the energy levels of the light after passing through the sample. The more C)2 in the sample, the more of the light that will be absorbed, and the weaker the IR signal will be when it reaches the sensor.

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Example of an IR CO2 sensor

The sensitivity of a CO2 sensor increases with the length of the light path through the sample gas. Thus the sensor used in Rotronic CO2 measuring devices makes use of multiple reflections of the IR beam on the walls of the probe chamber. this means the small CO2 sensor (2.5 cm x 5 cm) has a measuring path length of 12.5 cm and is accordingly sensitive. This type of sensor is called a NDIR (Non Dispersive Infra Red) sensor. This means that a broadband IR light source is used and the measured wavelength is filtered out at the end of the beam in front of the IR detector.

Why the Need to Measure CO2

New energy efficient demands lead to more airtight buildings and ventilation being completely turned off at night. Intelligent HVAC systems must be able to adapt themselves to situations with changing occupants of rooms. One answer is Demand Controlled Ventilation (DCV) with built-in CO2 sensors. By using DCV, huge amounts of energy can be saved without any drawback for the occupants. According to a study of the UN Climate Panel 40-50% of world energy is used in buildings. Only the adoption of the EU Directive on Energy Efficient Buildings would result in saving 30-45 MT of CO2/year. As HVAC (Heating, Ventilation and Air Conditioning) is responsible 40-65% of energy usage in commercial and public buildings, a balance between comfort and energy saving must be found.

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A large HVAC system

One example demonstrates the evidence of CO2 controlled room ventilation. The exhaled air of a human contains up to 40´000 ppm CO2. In one hour a person breathes out 15 litres of CO2. Thus in a classroom with a volume of 200 m³ occupied by 25 pupils the CO2 concentration increases in one hour by 1´875 ppm!

Especially in wine cellars, breweries, the beverage industry and other industries in which CO2 may be produced or processed the constant measuring of CO2 concentration is absolutely vital to prevent a deadly threat to the employees. This is not only a rational procedure but is also enforced by official regulations in nearly every developed country.

Philip Robinson                                                                                                       Rotronic UK

CO2… what’s it all about

In 2011 Rotronic expanded its range of measurement parameters to include Carbon Dioxide gas measurements and now provides a range of transmitters, loggers, large panel displays and handhelds.

CO2 is becoming an increasing important gas to monitor and control for several reasons. This post will explore some of the science, applications and future trends for this ubiquitous gas…

CO2 and Human Health

CO2 can seriously effect human health. Figure 1 shows this relationship and the possible implications.

Effects of CO2Figure 1 – CO2 levels 

Fresh air typically has around 350-450 ppm CO2 however in exhaled air levels increase to around 38,000 – 50,000ppm! Metabolism and exercise can increase the rate of CO2 production.

In the UK we typically have poorly ventilated buildings in addition with increasing drives for energy efficiency, buildings are becoming more air tight and if not managed carefully air change rates can be further reduced.  To demonstrate how quickly CO2 can rise through poor ventilation Figure 2 shows a log of CO2, Temperature and Humidity overnight in my bedroom! You can see levels quickly increase to >2400ppm. The rapid drop is due to an opened window

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Figure 2 – CO2 levels overnight (CO2 in ppm)

 

This direct relationship between CO2 and human occupation is a useful tool. It allows building management systems to control ventilation rates precisely to the levels required based on occupation rates. This can significantly reduce energy usage especially with the incorporation of variable speed fans.

Recent projects at Google’s Irish Headquarters and the Apple offices in Cork have used these principles to save energy and improve working conditions for their staff and achieve additional LEED points.

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Regulations are increasing for CO2 monitoring. Areas of interest especially we are seeing include Schools, Catering Areas and Car Parks.

If you have any queries relating to CO2 let us know!

Dr. Jeremy Wingate
Rotronic UK