CO2 sensors for Schools – Rotronic Success Story

Rotronic CO2 sensors installed in Högalidskolan school in Stockholm in August 2012

Högalidsskolan school, opened in 1921, is located on the beautiful hills of Southern Stockholm and is home to one of the so-called ”palace” schools. The building consists of the three blocks, A, B and
C. Whereas some years ago the school had to cater for the needs of 1100 (later 900) pupils between 6 and 16, this primary school now  hosts 660 pupils, since their numbers were reduced due to a planned
renovation costing 167 MSEK.

In a meeting with headmaster Mattias Boström we discussed the importance of the indoor climate in the school. Old buildings generally have a natural draft as ventilation, but energy savings and the call for a more comfortable indoor temperature during wintertime resulted in less natural draft and, as a consequence, higher CO2 emissions.

Schools have long ago introduced ventilation routines, but these are difficult to stick to especially during the winter season because ventilation means cooling. In order to quickly reach acceptable CO2 levels, the consultant fi rm MAKAB recommended the installation of CO2 sensors to measure proper CO2 values in all areas where pupils are working.

After the installation of stand-alone CO2 sensors (no regulation system needed) in all 36 classrooms, it can be seen that in some rooms the CO2 level quickly crosses the threshold of 1000 ppm. Now, teachers and pupils are regularly checking whether the red LEDs on the sensors are lit to indicate that the 1000 ppm limit is exceeded.

Sometimes it is impossible to vacate the room immediately for CO2 remediation, but the sensor also displays the actual CO2 value and rate of change and thus is very valuable. The response from teachers and pupils so far has been very positive and shows that the CO2 sensor is a practical tool for keeping the indoor climate at
an acceptable quality.

After the renovation, the building will be equipped entirely with a new ventilation system with an advanced filtering to reduce particles in the air. But there will still remain a need to regularly check on the CO2, temperature and humidity levels.

Dr. Jeremy Wingate
Rotronic UK

Water Activity and Moisture Content… What is the difference?

Water Activity and Moisture Content are two very different parameters which are often confused and misused.

In a meeting today with a manufacturer of coffee capsules and pods, these differences were critical.

– Their  whole bean supplier provided each batch with  moisture content readings.

– However customers buying the coffee capsules and pods were asking for detailed water activity measurements for each batch. In addition for BRC Food Safety and shelf life validation of the final product, water activity was required.

Why are there these differences and can one measurement be used to determine both values?

Moisture content is probably the simplest value to understand.  It is simply the quantity of water contained in a material. Traditionally measured through loss of weight on drying. This method raises some issues, depending on the drying temperature you may not remove all water or may also remove other non water compounds.

More modern methods resolve these issues and use infra red absorption. This way the water content is directly measured, the method is non-destructive and far quicker. 

Moisture content is typically given as a percentage in terms of weight.

Infrared Moisture Measurement
Infrared Moisture Measurement – A measure of moisture content through IR adsorption

 

Water Activity (aW) is a measure of the free water in a sample, and ranges between 0…1.  Pure water would have an aW of 1.0. As water activity measures the ‘free’ or ‘active’ water in a sample it is more relevant to growth of organisms, chemical processes, enzyme activity and physical parameters like size and clumping as these are only effected by the water that can be chemically interacted with. Interestingly Water Activity is related to Moisture Content but it is product and temperature specific.

aW… is more relevant to growth of organisms, chemical processes, enzyme activity and physical parameters

Rotronic HygroLab
Rotronic HygroLab Water Activity Measurement – A measure of the ‘free’ water

What is free water? Water can be bound in materials in two broad ways.

1. Chemically Bound Water. Is bound so tightly that it cannot be utilised by bacteria, enzymes etc. It can be removed  through high temperature heating.

2. Free Water. Is bound through weak bonds, structural diffusion, capillary condensation and surface binding. It can be utilised by bacteria and can exchange with the environment, it is also removed through heating.

For instance a whole grape would have the same moisture content as two halves of the same grape. However the aW would be far lower in a whole grape as much of the water is bound inside the grape skin and only made free when the grape is cut in half!

Take a look at our Water Activity white paper or our Knowledge base for more information.

Introduction to Water Activity

Water Activity White Paper and Product Overview

Application note F004 – Water activity in the food industry

 

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

CO2 record
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.

logos

 

 

 

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

Welcome…

It has to start somewhere and for the Rotronic UK blog this is it.

What we hope for this blog, is to start sharing with you the reader some of the more interesting and maybe in cases not so interesting things we come across day in day out as a supplier of measurement instruments, consultancy, training and calibration.

We have a mixed team with diverse interests and expertise, but we are all passionate about quality measurements providing the best solutions to our customers, partners and colleagues.

Please do comment and provide feedback (but be nice!).

Cheers

Jeremy.