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Walkthrough Investigations

Performing a Walkthrough Investigation as part of the Tools for Schools Process: 

Note: Before performing the walkthrough, the TfS committee should: 1. View the Walkthrough Investigation videotape; 2. Contact the local health director to invite their participation; 3) if your school has a central HVAC system, and is on a timer, make sure the system is on during the time you are conducting the walkthrough and checking air flow.

This meeting will be in the form of a walkthrough investigation of your school, both inside and outside of the building. The entire IAQ team and anyone else invited (head custodian, local health department sanitarian, ventilation expert, etc.) should participate in this key event. One person should be designated by the IAQ Coordinator to lead the investigation and another to write down notes of all findings.

Items needed include: Copies of the walkthrough checklist for each classroom, summary of checklists including either a floor-plan or list of all work areas and classrooms listing occupant reported IAQ irregularities, tools for opening parts of the ventilation system, a flashlight, a notebook to record findings, and, if available, carbon dioxide/carbon monoxide and temperature/relative humidity measurement instruments (thermometer, hydrometer) for spot checks of each classroom and work area when occupied during school hours. A yardstick with tissue taped to the top is useful to check ventilation.

The team should have already been trained about the utility and shortfalls associated with the use of IAQ measurement devices. Remember that all safety precautions should be heeded because parts of ventilation systems (fans, fan belts, motors, oil on the floor, overhead obstacles, exposed electrical wiring, etc.) can pose serious threats.

The walkthrough investigation is a comprehensive evaluation of the school building based on the summary of the checklists, what you have learned about IAQ, what you are able to learn by using your senses of sight, smell, feeling and hearing, and also what your measurement instruments may indicate. There are many ways to go about conducting the walkthrough investigation, but these steps are the ones that many schools have used with success.

  • Plan to spend about 3 minutes per classroom or office, 5 or more minutes for any area that is considered “problematic.”   If the roof is easily accessible, plan about half an hour or more to check the rooftop parts of the ventilation system, areas of poor rainwater drainage, sewer gas pipe locations, and other items on the ventilation checklist. Also plan to spend about half an hour walking outside of the school building to evaluate locations of intake air vents for each classroom and for the main air handlers, sources of potential outdoor pollution that can enter the building, and outdoor entrance mats and their effectiveness. The whole process can take from 2 to 5 hours depending on the size of your school, but do not take shortcuts since all the important decisions that the team will make concerning IAQ will be ultimately based on findings from this walkthrough investigation.
  • Assemble the team and invited participants at a time when school is in session and preferably at a time of the year considered the heating season (October – March). This scenario should provide the team with a good perspective of IAQ on a day when it is occupied and the school is dependent upon the mechanical ventilation system of the school. Generally, it is said that IAQ is worse during the winter months, so think of your investigation as evaluating the “worse case scenario”, even though this may not be the case.

Also keep in mind that the day you do your walkthrough may not be representative of what a typical day is like, so realize that your walkthrough results may need to be amended as new information comes forward. Before embarking on the investigation, be sure that someone is taking exhaustive notes of any problems as well as positive things that are mentioned. These notes will be written up and discussed later.

  • Using the checklists summary (each team member should have a copy), proceed in an organized fashion making sure to evaluate every classroom, office, hallway, work area, closet, air handling room, storage room, supply room, lounge, etc. in your school. As a guide for each area, have a copy of the checklists for each area with you because it is possible that a teacher or office worker, for example, may have missed something on their checklist.

Your main goal as investigators, however, is to evaluate the items on the summary pointed out by occupant of that area since the occupant knows his or her area better than anyone else and is most cognizant of what might be a problem. For the ventilation system aspects of the investigation, it is best to allow the person with the most expertise to take over at this point and allow him or her to evaluate the system using the ventilation checklist. The expert will not only determine if there are any problems, but should also explain to the team what the function of each part of the system is. Naturally, the system should be turned off prior to removing any panels and safety should be stressed at all times while inspecting these units.

  • While conducting the investigation, be generous in re-explaining to teachers and students what you are doing: “Our school’s indoor air quality team is conducting a walk-through investigation of every room in the school to make sure the air you are breathing is the best it can be.” Even remind the children to tell their parents what they saw at school today: “Tell your parents when you get home that there were some experts at our school today who were making sure the air we breathe is clean.” Parents should already know that the investigation is happening that day, but it is always a good idea to remind them.
  • If the team has acquired the use of IAQ measurement devices, use them cautiously since the results cannot be definitively relied on. Carbon dioxide levels, temperature and relative humidity (RH) change during the course of the day depending upon the level of occupation in a room, the timing of the ventilation system, time of day, etc. However, if at any time a level of carbon dioxide exceeds 1000 ppm, you can suspect a ventilation problem in that area and that further testing may be needed. Any level of carbon monoxide (CO) above 0 ppm is considered a problem. Your trainer should have instructed you about this.

  • Plan to follow up your walkthrough by contacting the teachers and other staff.   Consider providing teachers with a follow up letter thanking them for their participation, listing the problems found, the solution and the responsible party. 
                  Here is a good example:  Follow up Letter





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