NYC-WTC_000220400

NYC 9/11 Public Portal Document

Hillmann Environmental Group, LLC

4.6 Hydrogen Sulfide

Hydrogen sulfide is a colorless gas with a strong odor. This gas can be found during or after fires, and can cause varying complaints from headaches to nausea. The OSHA Permissible Exposure Limit (PEL) is 10 ppm. Levels of hydrogen sulfide in the subject space remained below the limit of detection of 1 ppm on all investigated days, and therefore below the recommended limits.

4.7 Oxygen

Oxygen is a normal and vital constituent of our atmosphere. The normal level of oxygen in air, at sea level, is 20.9%. If oxygen levels in a space are at or below 19.5%, the space is considered oxygen deficient (by OSHA 29 CFR Part 1910.94, 30 CFR Part 11 and ANSI Standard Z88.5-1973) and is unable to safely support human occupancy. The oxygen levels ranged from 20.7% to 21.2% in the subject space, and were within the recommended range.

4.8 Combustible Gasses

Combustible gasses are combustible, explosive and present a danger as such, especially when contained in a structure. Levels should mostly be below 1% and never exceed 10% in an occupied area. The LEL levels were below the limit of detection of 1.0% in the subject space at all times during the investigation.

4.9 Airborne Asbestos Fibers

Levels of airborne asbestos fibers ranged from below the limit of quantification to 0.005 fibers/cc. The EPA NESHAP standard is 0.01 fibers/cc. Observed levels were well below this limit. Bulk dust samples were also taken from various areas in the subject space to ensure cleaning procedures were effective after the World Trade Center collapse. Asbestos fibers were not detected in any of these samples.

4.10 Bulk Asbestos Samples

The U.S. EPA and NYSDEP define Asbestos Containing Materials (ACM) as any material containing greater than 1% asbestos. No asbestos was identified in the samples collected.

Cushman & Wakefield/44 Wall Street, New York, NY/Project Number N3-7476 Page 9

CITY_21MC1OO_OO238836O

NYC-WTC_00022041 1