NYC-WTC_000211000

NYC 9/11 Public Portal Document

Mr. Bernard P. Orlan May 30, 2002 Indoor Air Quality Assessment Page 3 P. S. S9M__________________________________ ATC Project No. 15-19125-0297 Real-Time Environmental Measurements

ATC collected seventy-nine (80) sets of real-time environmental measurements consisting of seventy (70) from inside the school building and ten (10) from outdoors. All five floors of the school building were surveyed. These results are described below.

Field data sheets are found in Attachment 1. Readings began at 8:00 A.M. and concluded at approximately 10:51 A.M.

Temperature

Indoor dry bulb temperature measurements ranged from 69.0 °F to 74.9 °F. Thirty-six (36) of the indoor measurements for temperature were below and none of the measurements were above the range of 73 to 79°F (at 50 percent relative humidity) as recommended by the ASHRAE Standard 55-1992 during the summer season. The outdoor temperature measurements was 68.6°F for all readings.

Relative Humidity

The relative humidity indoors ranged from 45.3 to 61.8 percent. One of the indoor measurements for relative humidity wa,s above and none of the measurements were below the ASHRAE-recommended range of 30 to 60 percent for occupant comfort. The outdoor relative humidity measurements was 65.3 percent for all readings.

Carbon Dioxide Concentration

Carbon dioxide concentrations indoors ranged from 598 ppm to 1750 ppm. Two (2) of the indoor measurements for CO2 were above the ASHRAE Standard 62-1999 recommended maximum concentration of <700 ppm above the background level. The maximum outdoor (background) CO2 concentration v/as 541 ppm. Therefore, the maximum acceptable level of CO2 at this location was 1241 ppm (background le\'el + 700 ppm). The highest reading was recorded in room 526 at 8:50 AM with 30 occupants. Carbon dioxide measurements are used as an indicator of available outside makeup air. The primary source of CO2 indoors is occupant respiration. The school building was occupied during ATC’s assessment.

Carbon Monoxide Concentration

Carbon monoxide concentrations indoors was 2 ppm for all readings. These concentrations were below the NPAAQS/ASHRAE guideline of 9 ppm. The outdoor CO concentrations was 2 ppm for all collected readings.

Rexpirahle Particulates (PM2 5)

Respirable particulate concentrations* indoors ranged between 6 pg/m^ to 30 pg/m^. The average PM2.5 concentration for the entire school building was approximately 15 pg/m^. All of the indoor measurements were below the NPAAQS of 65 pg/m^ 24-hour average concentration of particulate matter 2.5 micrometers or less in aerodynamic diameter and the USEPA recommended concentration of 40 pg/m^ for sensitive individuals and children. The outdoor

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