NYC-WTC_000227030

NYC 9/11 Public Portal Document

Temperature

Indoor dry bulb temperature measurements ranged from 69.4 °F to 75.8 °F. Four (4) measurement was above the range of 68 to 75°F (at 50 percent relative humidity) recommended by ASHRAE Standard 55-1992 during tire heating season (wintertime conditions), These measurements were collected from 4th floor. The outdoor temperature range was 48.5 to 53.0 °F.

Relative Humidity

The relative humidity indoors ranged from 17.4 percent to 29.7 percent. AH'measurements were below the ASHRAE-recommended range of 30 to 60 percent for occupant comfort. The outdoor relative humidity range was 16.9 and 22.5 percent.

Carbon Dioxide Concentration

Carbon dioxide concentrations indoors ranged from 465 ppm to 2015 ppm. Twelve (12) CO2 measurements were above the ASHRAE Standard 62-1999 recommended maximum concentration of <700 ppm above the background level. The outdoor (background) CO2 concentrations were 465 and 477 ppm. Therefore, the maximum acceptable level of CO2 at this location was 1177 ppm (background level + 700 ppm). The highest reading, 2015 ppm, was in Room 738. Rooms with CO2 levels above the recommended maximum were found on 4th, 5th, 7th and 9th floors. 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 0 ppm for all readings. These concentrations were below the NPAAQS/ASHRAE guideline of 9 ppm. The outdoor CO concentration was 0-1 ppm.

Respirable Particulates (PM2 5)

Respirable particulate concentrations* indoors ranged between 4 ng/m^ to 27 pg/m^. All measurements were below the NPAAQS of 65 pg/m^ 24-hour average concentration of particulate matter 2.5 micrometers or less in aerodynamic diameter. The outdoor respirable particulate concentrations were 29 and 35 pg/m^.

Filters with a higher efficiency rating were installed on the HVAC units that serve rooms on the 3rd, 4th, (5th and 7^^ floors (See Attachment 1). The PM2.5 concentration range for those rooms was 7-18 pg/m^ with an average of approximately 17 pg/m^. The PM2.5 concentration range for the other rooms was' 4-27 pg/m^ with an average of approximately 11 pg/m^. The average PM2.5 concentration for the entire school building was approximately 11 pg/m^. In addition to higher efficiency rating filters on their HVAC units, portable High Efficiency Particulate Air (HEPA) purifiers were placed in Rooms 327, 333, 638 and 740. The PM2 5 concentration range for these rooms was 7-18 pg/m^ with an average of approximately 11 pg/m^.

* Tire measurements made during this assessment were instantaneous readings, the NPAAQS is

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