PCE concentrations in indoor air can be reduced by adequate ventilation and air flow. But how much ventilation is needed? And is there enough air movement to reduce the PCE in your store?
Dry cleaners with PERC machines will have PCE concentrations in the air of their store because of the machines and the handling of PERC in your shop. But even drycleaners using new green machines probably have PCE in indoor air because there is PCE in the soil beneath the store emanating back up through cracks in the floor. The first step in controlling PCE exposure to your people is to provide adequate ventilation. The goal is to have 20 -50 room air changes per hour – that is to have enough ventilation to completely change out the volume of air in your shop 20 – 50 times per hour. This is accomplished through ceiling fans, air conditioning, and door fans. To calculate your air exchanges for yourself, first, calculate the volume of air in your shop. Measure the dimensions of your store – the length, the width and the height in feet – multiply these three dimensions to get the volume of air in your store in cubic feet. Then make a list of each ceiling fan, ac unit, and door fan and their flow rate in cfm (cubic feet per minute) – add up the total cfm for all of your fans and then multiply that number by 60 minutes in an hour to get your air flow. Divide your air flow number by the volume of air in your shop. This is your air exchanges per hour. If it is below 20, add some roof fans. If it is above 50, you have maximized your ventilation. Most public spaces change air 10 to 15 times per hour, smoking rooms change air 20 times per hour, and dry cleaners that want to reduce PCE concentrations in indoor air need to aim to change air 20 to 50 times per hour.