Connecticut Green LEAF Schools

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The Connecticut Green LEAF Schools program is a collaborative effort of the Connecticut Departments of Construction Services, Education, Energy and Environmental Protection and Public Health, as well as many Connecticut environmental and educational organizations created to promote green and healthy schools for all.  Find Out More About It: CT Green LEAF Schools




Outside air gets into school buildings either by natural ventilation (windows and doors) or a mechanical ventilation system (also known as Heating, Ventilation and Air Conditioning System- HVAC). Well-designed and properly operated school HVAC systems provide air at comfortable temperature and humidity levels and dilute harmful concentrations of indoor air pollutants. Most mechanical ventilation systems draw in outdoor air, mix it with indoor air, remove indoor air contaminants before distributing this mixed air throughout the school building, and then exhaust some portion of the indoor air outside. Indoor air quality (IAQ) problems may occur when any part of this process doesn’t work correctly.   Properly operated and maintained HVAC systems not only protect student and staff health, but also increase comfort and productivity. There is growing evidence that increased ventilation rates lead to higher reading and math scores and lower absentee rates.

 Some IAQ problems in schools occur because HVAC systems are poorly designed and/or constructed.   However, even the best-designed and well-constructed systems will not function well without proper operation and maintenance. The following ventilation practices are known to promote healthy and productive educational environments:

-     Do not locate contaminant sources close to air intakes (e.g. vehicle idling areas, plumbing and furnace exhaust ducts, garbage dumpsters, construction activities)

-    Ensure that all HVAC system components, including air handling units, controls and exhaust fans are easily accessible for maintenance

-   Operate the HVAC system continuously when the building is occupied

     -   Ventilate occupied areas at a minimum rate of 15 cubic feet per minute (cfm) per occupant

-   Maintain carbon dioxide (CO2) between 800 and 1000 parts per million (ppm)

-   Inspect and maintain the HVAC system and its components ( air intakes and exhausts, heating and cooling units, air filters, fans, belts, baffles, ceiling plenums and ductwork) on a regular basis

-   Change filters and clean drip pans according to manufacturer’s instructions (filters in high pollution areas may need to be serviced more frequently)

-   Ensure that air intakes and exhausts are not covered and/or blocked

-   Install local exhaust ventilation in bathrooms, janitors’ closets, food prep areas, science labs, art rooms, vocational workshops and copy/work rooms

-   Reconfigure the HVAC system after renovations

-   Test and balance the system every 5 years


Summary of CT LAWS dealing with ventilation in schools


(CT General Statutes Section Nos. 10-220 (a) and (d), 10-282 (19), 10-283 (b),

 10-286 (a) (9) and ( c) (2), 10-291, 10-231 e and f )


For all schools:

Requires a Board of Education to:

-     Ensure operation and maintenance of heating, ventilation and air conditioning (HVAC) systems in accordance with prevailing standards

-     Ensure operation of HVAC systems continuously while students and school staff occupy school facilities, with limited exceptions

-     Adopt and implement an IAQ program that provides for ongoing maintenance and facility reviews necessary for the maintenance and improvement of the IAQ of its facilities

-    Report every two years to the State Commissioner of Education on the condition of its facilities and on actions taken to implement its IAQ program

-    Keep HVAC maintenance records for at least 5 years.


For newer schools (constructed, extended, renovated or replaced after January 1, 2003):

-  Requires comprehensive inspections and evaluations by the local board of education, prior to January 1, 2008 and every five years thereafter, to detect    environmental problems. To be reviewed are HVAC and plumbing systems, radon levels, potential for exposure to microbial contaminants and chemical compounds, degree of pest infestation and pesticide usage, degree of moisture incursion, building cleanliness, building structural elements, use of space, presence of and plans for removal of hazardous substances and provision of IAQ maintenance training for staff.

-  Requires that these inspection reports be made public at a Board of   Education meeting


For schools being constructed, extended or replaced:. 

-   Requires the State Department of Education to deny approval of a school building project if the building maintenance staff is not trained in plant operation, including HVAC systems and IAQ issues.

-   Increasesthe maximum square footage per pupil limit for grant purposes by up to   1% to accommodate the HVAC system.




Question: Air testing was recently done at my son’s school and the CO2 reading in his room was 1468. What does that mean? 

Answer: Carbon Dioxide(CO2) is a gas that people breathe out.When CO2 levels exceed 1000 parts per million (ppm) it is an indication that there may be a problem with the ventilation system. Not enough fresh outside air is being brought into the room for the number of occupants in the room. To reduce CO2 build-up there should be 15 -20 cubic feet per minute (cfm) per person of fresh outdoor air being brought into the room. If CO2 is building up, so are other pollutants which are often difficult to measure. Concentrations of CO2 over 1000 ppm indicated crowded spaces or low ventilation rates. Even at elevated levels, it is usually not a hazardous pollutant.


Question: Are there any areas in a school that present unique ventilation challenges?

Answer: Art rooms, science labs and vocational workshops often use materials that are toxic or hazardous.   Without properly functioning local exhaust systems in these areas, the fumes and particulates generated there may become airborne and cause lung and eye irritations.   Contaminated air generated in these areas must not be circulated into the other parts of the building through the ventilation system.

 Copy/work rooms are another challenge. Copy machines and other office equipment off gas ozone and volatile organic compounds (VOCS) and should be well ventilated. This equipment is often placed in small unventilated spaces with people working nearby. Ozone and VOCs are harmful to lung function.


Question: What ventilation problems have you found during a school walkthrough inspection?

Answer: I am the Tools for Schools Coordinator for my school district. Most of the ventilation problems that my school teams found were easy fixes, but there were a few issues that presented much more of a problem. The quick and cheap fixes included:

-   Furniture and teaching supplies blocking ducts or vents were moved.

-   Windows that wouldn’t open were repaired.

-    Photocopiers and other equipment that produce exhausts were poor located, resulting in fumes moving toward occupants instead of away from them. They were moved under exhaust vents that drew fumes away from people.

-    Blocked fresh air intakes were unblocked.

-    Many HVAC controls were set to AUTO rather than ON. School personnel were instructed to leave controls in the ON position, so that the fan continuously brings in outside air. In the AUTO position, the fan shuts off when the temperature settings are reached. Signs were posted next to controls with instructions to LEAVE ME ON!

-    Fans that were running backwards were fixed.

-    Ventilation systems that were turned off or left off for long periods of time were turned back on and signs were posted to leave them on.


The more challenging ventilation problems all came after renovations. One wing in an elementary school was missing all the ductwork for the exhaust system. In the high school, the science and computer wings were renovated so that air vents ended up between new dropped ceilings and the original ceilings, allowing for no ventilation in these areas. In the Metal Shop at the high school, the welding hood exhaust was vented into the hallway of the math/shop wing instead of outside. These problems were found many years after the renovations had been completed and cost thousands of dollars to fix.




EPA Tools for Schools Ventilation Basics Video:


 EPA IAQ Tools for Schools Kit Background Information for Ventilation Checklist:


EPA IAQ Tools for Schools Kit Ventilation Checklist:


EPA IAQ Design Tools for Schools section on HVAC Systems:


EPA Indoor Air Quality Scientific Findings Resource Bank on the Health and Economic Impacts of Building Ventilation:


EPA Duct Cleaning Information:


CT Department of Public Health IEQ Section on Ventilation:|#Ventilation


EPA Ventilation and Air Quality in Offices:


WashingtonStateSchool IAQ Best Practices Manual:


CT Tools for Schools Heroes