NYC-WTC_000226988

NYC 9/11 Public Portal Document

Mr. Bernard P. Orlan January 28, 2002 Air Sampling for Silica Dust Page 2 Stuyvesant High School ATC Project No. 15-19125-0246

Air Sample Results

No silica was reported above the detection limits in any of the samples obtained on December 7, 2001 and January 4, 2002.

Two samples were reported to be above the detection limit on the sampling date of January 9, 2002. Sample number ATC-0109-STY-S6 (obtained from the 2"^ floor lobby) was reported to be 0.0147 milligrams per cubic meter of air (mg/m') and sample number ATC-0109-STY-S7 (obtained from Room 260 East) was reported to be 0.0135 mg/m’.

The Occupational Safety and Health Administration (OSHA) Permissible Exposure Lirnit (PEL) for silica-containing dust is based on the percent of quartz (SiO2) found in the dust, the higher the percentage of quartz, the lower the PEL. The formula for calculating the PEL is found in 29 CFR 1910.1000, Table Z-3. The formula is: lOmg/m’ %SiO2 + 2

The amount of quartz in Sample #ATC-0109-STY-S6 was <24%, therefore the PEL for this dust would be: lOmg/m’ 0.385 mg/m’ 24 + 2

The silica concentration in this sample was 0.0147 mg/mg^, which is 3.8% of the calculated PEL.

The amount of quartz in Sample #ATC-0109-STY-S7 was <22%, therefore the PEL for this dust would be: lOmg/m’ = 0.417 mg/m’ 22 + 2

The silica concentration in this sample was 0.0135 mg/mg^, which is 3.2% of the calculated PEL.

ATC appreciates the opportunity to provide this indoor air quality consultative service to the BOE. Please call me at (212) 353-8280 extension 212 if you have any questions.

Sincerely, ATC Associates, Inc.

James R. Cohn, CIH, CSP Regional Manager Industrial Hygiene Division

Attachment

CITY_21MC100_002896986

NYC-WTC_000226989