NIOSH Publication No. 2005-151:

NIOSH Pocket Guide to Chemical Hazards

September 2005

Silicon

CAS
7440-21-3

Si

RTECS
VW0400000
Synonyms & Trade Names

Elemental silicon [Note: Does not occur free in nature, but is found in silicon dioxide (silica) & in various silicates.]
DOT ID & Guide
1346 / 170 (amorphous powder)

Exposure
Limits

NIOSH REL: TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
OSHA PEL: TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp)
IDLH
N.D. See: IDLH INDEX
Conversion
Physical Description
Black to gray, lustrous, needle-like crystals. [Note: The amorphous form is a dark-brown powder.]
MW: 28.1
BP: 4271°F
MLT: 2570°F
Sol: Insoluble
VP: 0 mmHg (approx)
IP: NA

Sp.Gr(77°F): 2.33
Fl.P: NA
UEL: NA
LEL: NA
MEC: 160 g/m3
Combustible Solid in powder form.
Incompatibilities & Reactivities

Chlorine, fluorine, oxidizers, calcium, cesium carbide, alkaline carbonates
Measurement Methods
NIOSH 0500, 0600
See: NMAM or OSHA Methods
Personal Protection & Sanitation
(See protection)
Skin: No recommendation
Eyes: Prevent eye contact
Wash skin: No recommendation
Remove: No recommendation
Change: No recommendation

First Aid
(See procedures)
Eye: Irrigate immediately

Breathing: Fresh air
Swallow: Medical attention immediately
Respirator Recommendations
Not available.
Important additional information about respirator selection
Exposure Routes
inhalation, ingestion, skin and/or eye contact
Symptoms
Irritation eyes, skin, upper respiratory system; cough
Target Organs
Eyes, skin, respiratory system
See also: INTRODUCTION