NYC-WTC_000219855

NYC 9/11 Public Portal Document

Mr. Bernard P. Orlan May 3, 2002 Indoor Air Quality Assessment Page 3 H.S. of Economics and Finance (M833)________ ATC Project No. 15-19125-0291 Real-Time Environmental Measurements

ATC collected one hundred (100) sets of real-time environmental measurements consisting of eighty-eight (88) inside the school building and twelve (12) outdoors. Field data sheets are found in the Attachment. Readings were collected between morning to evening. The results are described below.

Temperature

Indoor dry bulb temperature measurements ranged from 63.5 °F to 77.0 °F. Nineteen (19) measurements were below and sixty-nine (69) measurements were within the range of 73 to 79°F (at 50 percent relative humidity) recommended by ASHRAE Standard 55-1992 during the summer season. The outdoor temperature measurements ranged from 58.9 °F to 67.1 °F.

Relative Humidity

The relative humidity indoors ranged from 42.7 percent to 65.5 percent. Three (3) of the indoor measurements for relative humidity were above and eighty-five (85) measurements were within the ASHRAE recommended range of 30 to 60 percent for occupant comfort. The outdoor relative humidity ranged from 45.0 to 64.6 percent.

Carbon Dioxide Concentration

Carbon dioxide concentrations indoors ranged from 539 ppm to 2040 ppm. Eleven (11) of the indoor measurements for CO2 were above the ASHRAE Standard 62-1999 recommended maximum concentration of <700 ppm above the background level. The outdoor (background) CO2 concentration was 480 ppm. Therefore, the maximum acceptable level of CO2 at this location was 1180 ppm (background level + 700 ppm). The highest reading (2040 ppm) was measured in Staircase A around 11:25 AM. Levels above the recommended maximum do not indicate a health risk. Carbon dioxide measurements are used as an indicator of available outdoor air. The primary source of CO2 indoors is occupant respiration.

Carbon Monoxide Concentration

Carbon monoxide concentrations indoors ranged from 0 ppm to 1 ppm. These concentrations were below the NPAAQS/ASHRAE guideline of 9 ppm. The outdoor CO concentrations ranged from 1 ppm to 13 ppm.

Respirable Particulates (PM2 5)

Respirable particulate concentrations* indoors ranged between 6 pg/m^ to 95 pg/m3 with an average 22 pg/m^- One (1) of the indoor measurements for respirable particulates was above the NPAAQS of 65 pg/m^ 24-hour average concentration of particulate matter 2.5 micrometers or less in aerodynamic diameter. Five (5) of the eighty-eight (88) indoor instantaneous measurements were above the USEPA recommended concentration of 40 pg/m^ for sensitive individuals and children. The outdoor respirable particulate concentration ranged from 38 pg/m^ to 134 pg/m^ with an average of 75 pg/m^. Six (6) of the outdoor measurements for respirable particulates were above the NPAAQS of 65 pg/m^ 24-hour average concentration of particulate matter 2.5 micrometers or less in aerodynamic diameter. Eleven (11) the twelve (12) outdoor

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NYC-WTC_000219857