This paper is based on findings resulting from ASHRAE Research Project RP-1083.

This research focuses on measuring the off-gassing of disinfection by-products (DBP’s) from chlorine-based pool water treatment, filtration and chemistry of an indoor test swimming pool, to provide the Mechanical System Designer with specification guidelines for improved air quality. Aqueous derived effluent from the mechanical dehumidification (MDH) system is analyzed for chloroform (a trihalomethane or THM), chloramines and pH using commercially available products. Pool vapor content and composition are determined by gas chromatography using standard NIOSH and OSHA analytical methods and includes preliminary nitrogen trichloride (trichloramine or TCA) measurement using published methods. Based on observation, this research confirms and highlights that nitrogen trichloride is the vapor (gas) that causes the most irritation and pool air containing TCA is essentially toxic over long term exposure. Tests conducted with top level ventilation and re-circulation rates confirmed the need to understand Henry’s Law and the physical properties of TCA. When used in conjunction with deck (ground) level ventilation, low exhaust air movement at ASHRAE’s current ventilation rate (0.5 cfm/ft²) can be successful in maintaining this heavier than air TCA gas at low levels within the indoor space.

Units: I-P