NYC-WTC_000207776

NYC 9/11 Public Portal Document

Mr. Bernard P. Orlan September 6, 2002 Indoor Air Quality Assessment Page 3 P.S.42M ATC Project No. 15-19125-0342

Real-Time Environmental Measurements

ATC collected fifty (50) sets of real-time environmental measurements consisting of forty-eight (48) in the school building and two (2) outdoors. All floors of the school were surveyed. Field data sheets are found in the Attachment. Readings were collected during school hours. The results are described below.

Temperature

Indoor dry bulb temperature measurements ranged from 73.3 to 79.9 °F. Nine (9) of the indoor temperature measurements were above the range of 73 to 79 °F (at 50 percent relative humidity) recommended by ASHRAF Standard 55-1992 during the summer season. The outdoor temperature measurements were 78.1 and 79.9 °F.

Relative Humidity

The relative humidity indoors ranged from 49.2 percent to 79.3 percent. Thirty-eight (38) of the indoor measurements for relative humidity were above the ASHRAE-recommended range of 30 to 60 percent for occupant comfort. The outdoor relative humidity measurements were 71.4 and 78.8 percent. The high ambient relative humidity likely contributed to the elevated particulate levels reported below'.

Carbon Dioxide Concentration

Carbon dioxide concentrations indoors ranged from 494 ppm to 819 ppm. All indoor measurement for CO2 were below the ASHRAE Standard 62-2001 recommended maximum concentration of <700 ppm above the background level. The average outdoor (background) CO2 concentration was 535 ppm. Therefore, the maximum acceptable level of CO2 at this location was 1235 ppm (background level -1- 700 ppm). Carbon dioxide measurements are used as an indicator of available outdoor air. The primary source of COg indoors is occupant respiration.

Carbon Monoxide Concentration

Carbon monoxide concentrations indoors ranged from 1 ppm to 3 ppm. These concentrations were below the NPAAQS/ASHRAE guideline of 9 ppm. The outdoor CO concentrations were 2 ppm and 4ppm.

Respirable Particulates (PM2,5)

Respirable particulate concentrations* indoors ranged between 81 pg/m^ to 315 pg/m^. All of the indoor measurements collected for PM2_5 were above the USEPA recommended concentration of 40 pg/m^ for sensitive individuals such as asthmatic people and children. At the time of ATC’s site visit there was construction going on outside the building. The two outdoor respirable particulate concentrations were 232 pg/m^ and 312 pg/m^ with an average of 272 pg/m^. The Dust Trak® detects volatile aerosol particles and may be affected by elevated humidity and airborne moisture droplets in addition to dust particles.

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