Indoor Air Quality in Schools:
The importance of Monitoring Carbon Dioxide Levels
Section 2

Discussion of Monitoring Details
A graph of the monitoring results is presented in Figure 1. The locations depicted in this graph were mostly in the immediate area of the AIRxpert System's booth-one was approximately 50 feet away at the central aisle, between rows 200 and 300.

As can be observed from this data, the CO2 concentration was around 600 parts per million (PPM) at the time sampling began at around 2:00 p.m. on Tuesday, November 12, 2002. This CO2 concentration in the Exhibit Hall increased to about 730 PPM while the exhibitors prepared their booths. By 5:30 p.m., when the Opening Reception in the Exhibit Hall had been underway for 30 minutes, the CO2 concentrations had already begun to rapidly increase. This CO2 concentration increase continued throughout this event, eventually reaching values of almost 1,700 PPM by the time the event ended.

In order for the CO2 concentration in this space to increase this high over the outdoor conditions of about 400 PPM, the ventilation would have to be no more than 8 CFM of outdoor air per person. The mathematical relationship between the increase of CO2 concentrations indoors over outdoors assumes that equilibrium conditions have been achieved. In the absence of these steady-state conditions, this calculation yields an estimate of the ventilation rate that is greater than is really being provided. Consequently, this ventilation rate determination is reported as no more than 8 CFM. This value is clearly less than the ASHRAE recommended minimum of 15 CFM of outdoor air, so a ventilation deficiency exists.

After the event ended and the hall emptied out at approximately 8:00 p.m., the CO2 concentration decreased down to less than 900 PPM. For some reason this CO2 concentration began increasing again in the late evening, perhaps, because of housekeeping activities, and rose to over 1,100 PPM. Overnight the CO2 concentration slowly decreases down to almost 700 PPM. It then quickly dropped to around 630 PPM, presumably when the HVAC system came on. The CO2 concentration began increasing again as people started to enter the Hall. This overnight monitoring data reveals another aspect of the Exhibit Hall's ventilation deficiency --- the failure of the system to flush the space out before occupancy begins the next day.

About the Authors

David Sundersingh is a LEED 2.0 Accredited Professional at Fanning/Howey Associates, Inc., and David W. Bearg is an independent mechanical engineer.

David Sundersingh
Fanning/Howey Associates, Inc
1200 Irmscher Blvd.
Celina, OH 45822
419-586-2292
dsundersingh@fhai.com

Figure 1. Graph of Monitoring Data

During the late morning of Wednesday, November 13, 2002, a meeting with the HVAC operators was arranged to communicate this information about the ventilation system's performance. As a result, the position of the outdoor air dampers was increased around noon on this day. The change in ventilation rate resulting from this damper position change was quickly observable. The CO2 concentration decreased in the Hall down to around 530 PPM by 1:30 p.m., and its peak around 6:00 p.m. was only around 800 PPM in the early evening. The Exhibit Hall closed at 7:00 p.m. that evening. The upper limit to the ventilation rate could now be calculated to be 26 CFM per person, far more conducive to keeping exhibitors and visitors awake and alert in this now healthier and more productive environment. The overnight purge was also much improved with the CO2 concentration decreasing to around 470 PPM by midnight. These monitoring results also raise questions about the appropriateness of the CO2 set point controlling the air handlers, as well as the lack of any assessment to make sure that the system was working as intended to provide a given amount of ventilation to the space's occupants.

Performance Loss Evaluated (EPA 402-F-00-009)

An EPA document (http://www.epa.gov/iaq/schools/images/perform.pdf) gives the following findings:

• a study was done in Europe, involving 800 students from eight different schools, to measure student performance related to indoor air quality.
• The data collected indicated health symptoms and the student's ability to concentrate as related to CO2 measurements in the classroom.
• The students were given a health symptom questionnaire on which to record the data, and a computer-based program scored their ability to concentrate.
• In classrooms where CO2 levels were high (low ventilation rates), students' scores were low and their health symptoms responses were high.
• The data also concluded that poor IAQ could reduce one's ability to perform specific mental tasks requiring concentration, calculation, or memory.
• The tests were statistically significant and tend to confirm that, with IAQ management including source control and adequate ventilation, student performance can improve.

The main source of CO2 is from exhaled breath and the main mechanism to remove it is by ventilation. High levels of CO2 in classrooms are an indication of low rates of ventilation. Proper monitoring of CO2 levels can correct this to give the space a good indoor air quality.

Lessons to be Learned
Given the fact that indoor air is invisible, it is always a challenge to properly design for both quality and quantity. CO2 levels give a good idea of the quality of indoor air. Monitoring of CO2 levels is a necessity for knowing the quality of the indoor air in any space. When the space is an instructional space, especially when the facility houses an early childhood learning environment, the need is even greater, since young children are the most vulnerable to the effects of poor indoor air quality. Innovative mechanical engineers have always designed for higher values of CFM (cubic feet per minute) than required just to make sure that there is more ventilation than the prescribed minimum. In the 1960's it was not uncommon to design for indoor air at the rate of 30 CFM per person; this dropped to 5 CFM at the time of the first energy crisis in the early 1970's. We have over time reached 15 CFM. The question is, "Do we always have to design for the minimums? Shouldn't we be designing systems to achieve the higher values needed by children?" Innovative system designers will be proactive in utilizing higher ventilation rates to ensure that indoor air is of the highest quality. CO2 monitoring is a must for maintaining that high quality in the classroom.

Owners, architects, and engineering professionals have benefited thus far by the efforts of the U.S. Green Building Council, which has supplied the building community with facts and figures on the benefits of "green" buildings. Since the average life of a well-designed school is between forty and sixty years, it is important that educational facility planners and educational architects assist in educating school officials and their communities on the latest in "green design," so that they will be open to design issues that address indoor air quality for the children that they ultimately serve. The next step is to establish appropriate design criteria for learning environments.

Can we aspire to improve our indoor air quality? Will the United States Green Building Council be proactive in its next round of LEED rating system criteria and give more credit and points for achieving better indoor air quality? Will the USGBC define ventilation levels and better monitoring of indoor air quality at the correct breathing zone for children? We say that we want to leave a better place for our children and future generations. Are we serious about a higher ideal of excellent indoor air quality in the future? The future is here… Are we willing to change?

David Bearg, PE, CIH
20 Darton Street
Concord, MA 01742-5710
Tel: 978-369-5680
david.bearg@airxpert.com