# NIOSH Pocket Guide to Chemical Hazards
Hafnium | CAS 7440-58-6
Hf | RTECS MG4600000
Synonyms & Trade Names Celtium, Elemental hafnium, Hafnium metal | DOT ID & Guide 1326 170 (powder, wet) 2545 135 (powder, dry)
Exposure Limits | NIOSH REL*: TWA 0.5 mg/m3 [*Note: The REL also applies to other hafnium compounds (as Hf).]
OSHA PEL*: TWA 0.5 mg/m3 [*Note: The PEL also applies to other hafnium compounds (as Hf).]
IDLH 50 mg/m3 (as Hf) | Conversion
Physical Description Highly lustrous, ductile, grayish solid.
MW: 178.5 | BP: 8316°F | MLT: 4041°F | Sol: Insoluble
VP: 0 mmHg (approx) | IP: NA |  | Sp.Gr: 13.31
Fl.P: NA | UEL: NA | LEL: NA |
Explosive in powder form (either dry or with <25% water); finely divided powder can be ignited by static electricity or even SPONTANEOUSLY.
Incompatibilities & Reactivities Strong oxidizers, chlorine
Measurement Methods NIOSH S194 (II-5); OSHA ID121
Personal Protection & Sanitation Skin: Prevent skin contact Eyes: Prevent eye contact Wash skin: When contaminated/Daily Remove: When wet or contaminated Change: Daily Provide: Eyewash, Quick drench | First Aid (See procedures) Eye: Irrigate immediately Skin: Soap wash promptly Breathing: Respiratory support Swallow: Medical attention immediately
Respirator Recommendations NIOSH/OSHA Up to 2.5 mg/m3: (APF = 5) Any dust and mist respirator Up to 5 mg/m3: (APF = 10) Any dust and mist respirator except single-use and quarter-mask respirators/(APF = 10) Any supplied-air respirator Up to 12.5 mg/m3: (APF = 25) Any supplied-air respirator operated in a continuous-flow mode*/(APF = 25) Any powered, air-purifying respirator with a dust and mist filter* Up to 25 mg/m3: (APF = 50) Any air-purifying, full-facepiece respirator with a high-efficiency particulate filter/(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 50 mg/m3: (APF = 2000) Any supplied-air respirator that has a full facepiece and is 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 a high-efficiency particulate filter/Any appropriate escape-type, self-contained breathing apparatus
Exposure Routes inhalation, ingestion, skin and/or eye contact
Symptoms In animals: irritation eyes, skin, mucous membrane; liver damage
Target Organs Eyes, skin, mucous membrane, liver
See also: INTRODUCTION