NYC-WTC_000220400

NYC 9/11 Public Portal Document

Hillmann Environmental Group, LLC

SECTION 4 - DISCUSSION

While on site, Hillmann performed various types of air sampling and observed work conditions.

4.1 Temperature

The American Society of Heating, Refrigeration and Air-conditioning Engineers (ASHRAE) recommends temperatures be kept between 66°F and 76°F. In the occupied space, temperatures ranged from 69‘’F to 78®F, and were above the recommended range in many areas.

4.2 Relative Humidity

ASHRAE recommends relative humidity range between 39% to 69%. Relative humidity levels in the subject space ranged from 39% to 64% and were above the recommended range in some areas.

4.3 Carbon Dioixide

ASHRAE recommends carbon dioxide levels remain below an outdoor reading plus 700 ppm. The outdoor readings ranged from 521 ppm to 535 ppm, therefore the recommended limits were 1221 ppm to 1235 ppm. Carbon dioxide levels ranged from 521 ppm to 1044 ppm. Carbon dioxide levels did not exceed the recommended range.

4.4 Carbon Monoxide

Carbon monoxide, a colorless, odorless gas, is a by-product of incomplete combustion. Carbon monoxide combines with hemoglobin in the blood to cause carboxyhemoglobin poisoning, Carbon monoxide can be released by many different sources such as: motor vehicle exhaust (intakes for the ventilation system located near a loading dock), tobacco smoke, and cracked exchangers on gas-fired heating appliances. The standards for Carbon Monoxide are the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) of 35 ppm, the Occupational Safety and Health Administration (OSHA) Permissible Exposure Level (PEL) of 35 ppm, and the Environmental Protection Agency (EPA) Natiorial Ambient Air Quality Standard (NAAQS) of 9 ppm. Carbon monoxide levels measured in the occupied areas ranged from below the limit of detection of 1 ppm to 2 ppm, and were below the recommended limits.

4.5 Volatile Organic Compounds

Volatile organic compounds are carbon-containing compounds that boil at temperatures low enough that they can become gasses under normal conditions. They are frequently used as solvents and cleaners and can be given off by such materials as plastics and wiring insulation, especially if these materials are heated. Volatile organic compounds were measured by Photo Ionization Detector (P.I.D.). Hillmann recommends that levels detected by P.I.D. remain below three times the outdoor reading. Since the outdoor reading was below the limit of detection of 0.1 ppm, the recommended limit would be 0.3 ppm. In the subject space, levels were found to range from below the limit of detection of 0.1 ppm to 7.4 ppm. Levels measured by P.I.D. remained below this limit except for one reading in the Penthouse. However, this elevated reading can be attributed to adjacent roofing work that was occurring at the time of the investigation. A follow-up reading showed that levels had returned to normal.

Cushman & Wakefield/44 Wall Street, New York, NY/Project Number N3-7476 Page 8

CITY_21MC100_002388359

NYC-WTC_000220410