NYC-WTC_000199213

NYC 9/11 Public Portal Document

Mr. Bernard P. Orlan May 28, 2002 Indoor Air Quality Assessment Page 3 P. S. 234M ATC Project No. 15-19125-0279

Real-Time Environmental Measurements

ATC collected sixty (60) sets of real-time environmental measurements consisting of fifty-one (51) from inside the school building and nine (9) outdoors. All three floors of the school were surveyed. These results are described below.

Field data sheets are found in Attachment 1. Readings began at 2:00 P.M. and concluded after 4:30 P.M.

Temperature

Indoor dry bulb temperature measurements ranged from 68.0 °F to 74.6 °F. Thirty (30) indoor measurements for temperature were below and twenty-one (21) of the measurements were within the range of 73 to 79°F (at 50 percent relative humidity) as recommended by ASHRAE Standard 55-1992 during the summer season. The outdoor temperature measurements ranged from 61 to 69 °F.

Relative Humidity

The relative humidity indoors ranged from 35.6 percent to 44 percent. All of the indoor measurements for relative humidity were within the ASHRAE-recommended range of 30 to 60 percent for occupant comfort. The outdoor relative humidity ranged from 44 to 47.6 percent.

Carbon Dioxide Concentration

Carbon dioxide concentrations indoors ranged from 545 ppm to 955 ppm. All of the measurements were below the ASHRAE Standard 62-1999 recommended maximum concentration of <700 ppm above the background level. The maximum outdoor (background) CO2 concentration was 555 ppm. Therefore, the maximum acceptable level of CO2 at this location was 1255 ppm (background level + 700 ppm). 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 were 1 ppm for all readings. These concentrations were below the NPAAQS/ASHRAE guideline of 9 ppm. The outdoor CO concentrations were 1 ppm for all readings.

Respirable Particulates (PM2 5)

Respirable particulate concentrations* indoors ranged between 18 pg/m^ to 50 pg/m^ with an average approximately 30 pg/m^- None of the measurements collected indoors for respirable particulate concentrations were above the NPAAQS 65 pg/m^ 24-hour average concentration of particulate matter 2.5 micrometers or less in aerodynamic diameter. Four (4) of the fifty-one (51) instantaneous readings were above the USEPA recommended concentration of 40 pg/m^ for sensitive individuals and children. The outdoor respirable particulate concentration ranged from 79 pg/m3 to 90 pg/m^ with an average of approximately 82 pg/m^.

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NYC-WTC_000199215