NIOSH Publication No. 2005-151:

NIOSH Pocket Guide to Chemical Hazards

September 2005

Silica, amorphous

CAS
7631-86-9

SiO2

RTECS
VV7310000
Synonyms & Trade Names

Diatomaceous earth, Diatomaceous silica, Diatomite, Precipitated amorphous silica, Silica gel, Silicon dioxide (amorphous)
DOT ID & Guide

Exposure
Limits

NIOSH REL: TWA 6 mg/m3
OSHA PEL: TWA 20 mppcf (80 mg/m3/%SiO2)
IDLH
3000 mg/m3 See: 7631869
Conversion
Physical Description
Transparent to gray, odorless powder. [Note: Amorphous silica is the non-crystalline form of SiO2.]
MW: 60.1
BP: 4046°F
MLT: 3110°F
Sol: Insoluble
VP: 0 mmHg (approx)
IP: NA

Sp.Gr: 2.20
Fl.P: NA
UEL: NA
LEL: NA

Noncombustible Solid
Incompatibilities & Reactivities

Fluorine, oxygen difluoride, chlorine trifluoride
Measurement Methods
NIOSH 7501
See: NMAM or OSHA Methods
Personal Protection & Sanitation
(See protection)
Skin: No recommendation
Eyes: No recommendation
Wash skin: No recommendation
Remove: No recommendation
Change: No recommendation

First Aid
(See procedures)
Eye: Irrigate immediately

Breathing: Fresh air

Respirator Recommendations
NIOSH
Up to 30 mg/m3:
(APF = 5) Any quarter-mask respirator. Click here for information on selection of N, R, or P filters.
Up to 60 mg/m3:
(APF = 10) Any particulate respirator equipped with an N95, R95, or P95 filter (including N95, R95, and P95 filtering facepieces) except quarter-mask respirators. The following filters may also be used: N99, R99, P99, N100, R100, P100. Click here for information on selection of N, R, or P filters.
(APF = 10) Any supplied-air respirator
Up to 150 mg/m3:
(APF = 25) Any supplied-air respirator operated in a continuous-flow mode
(APF = 25) Any powered air-purifying respirator with a high-efficiency particulate filter.
Up to 300 mg/m3:
(APF = 50) Any air-purifying, full-facepiece respirator with an N100, R100, or P100 filter. Click here for information on selection of N, R, or P filters.
(APF = 50) Any supplied-air respirator that has a tight-fitting facepiece and is operated in a continuous-flow mode
(APF = 50) Any powered, air-purifying respirator with a tight-fitting facepiece and a high-efficiency particulate filter
(APF = 50) Any self-contained breathing apparatus with a full facepiece
(APF = 50) Any supplied-air respirator with a full facepiece
Up to 3000 mg/m3:
(APF = 1000) Any supplied-air respirator operated in a pressure-demand or other positive-pressure mode
Emergency or planned entry into unknown concentrations or IDLH conditions:
(APF = 10,000) Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode
(APF = 10,000) Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained positive-pressure breathing apparatus
Escape:
(APF = 50) Any air-purifying, full-facepiece respirator with an N100, R100, or P100 filter. Click here for information on selection of N, R, or P filters./Any appropriate escape-type, self-contained breathing apparatus
Important additional information about respirator selection
Exposure Routes
inhalation, skin and/or eye contact
Symptoms
Irritation eyes, pneumoconiosis
Target Organs
Eyes, respiratory system
See also: INTRODUCTION