Covid-19: guide to properly ventilate classrooms

With the return to school , the correct ventilation of the spaces becomes another fundamental measure to prevent the classrooms from becoming areas of high risk for contagion.
For this reason, Harvard University has designed a guide with five easy steps to properly ventilate a classroom or specific space.

We teach it to you.

1. Measure the classroom

We measure the dimensions of the classroom with a laser pointer or tape measure using the following formula: length x width x height .

2. Pre-check of the ventilation system

Before each class, we will check that the ventilation systems are turned on and are working properly . To do this, the sound emitted by the equipment will be heard and with a piece of thin cloth the direction of the air flow will be observed (for example, if the equipment is supplying or extracting air).

Covid19: guide to properly ventilate classrooms

3. Measure or estimate the outdoor air ventilation rate

The third Harvard guide will depend on the ventilation system installed and the classroom situation. The objective is to measure the circulation of the outside air through the ventilation system. The guide provides us with three indications :

– We must choose a capture hood for the ballometer with the closest form factor to cover air diffusers, that is, choose a hood that is similar to the shape of the air diffuser. If the bill hood doesn’t cover the entire diffuser, we’ll use a piece of cardboard and tape to direct the flow through the capture hood.

– Start outside and use the ballometer to measure the air flow (in m 3 per minute) entering the building through the grille through which the air is drawn in.

– Inside the classroom, we will use the ballometer to measure the air flow in the air diffusers from where air is supplied or blown into the room.

4. Check results and objectives

The goal we seek is to produce at least five air changes per hour. It is the amount stipulated, according to the guide, within the American standard ASHRAE 62.1 for classrooms (in elementary and secondary schools) of approximately 25 students per 100 square meters .

5. Complementary measures to achieve the objective

If we do not achieve the above objectives or we want to increase and improve ventilation, the guide provides us with complementary measures. For example, use MERV-13 type filters for recirculated air and install portable air purifiers with HEPA filters to minimize the risk of transmission.

We must bear in mind that opening doors and windows favors the renewal and circulation of air, but, in no case, does it replace the regular check of the ventilation systems and units.

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