What Are the Exposure Limits for Aerogel Dust?

The US OSHA standard for amorphous silica is: (80 mg/m3)/(%SiO2). The NIOSH Sampling Method 7501 for Amorphous Silica calculates the %SiO2 based on the percentage of crystalline silica in the sample. Because the percentage of crystalline silica in aerogel is 0%, OSHA’s particulate limits of 15 mg/m3 (total dust) and 5 mg/m3 (respirable dust) apply to Aerogel exposure. The US National Institute for Occupational Safety & Health (NIOSH) standard for amorphous silica is 6 mg/m3. The German MAK for amorphous silica is 4 mg/m3 (inhalable fraction).

The American Conference of Governmental Industrial Hygienists (ACGIH) withdrew their threshold limit values (TLV) for amorphous silica in 2005 due to insufficient data on singlesubstance exposure. The withdrawn ACGIH TLVs which included co-exposure with crystalline silica were: 10 mg/m3 (total dust) and 3 mg/m3 (respirable dust). The ACGIH recommendations for Particles (insoluble or poorly soluble) Not Otherwise Specified [PNOS] are maintaining airborne concentrations below 3 mg/m3, respirable particles, and 10 mg/m3, inhalable particles.

During industrial hygiene studies conducted during Aerogel fabrication operations, total dust concentrations ranged from 0.44 to 4.6 mg/m3 and respirable dust concentrations ranged from <0.15 to 1.2 mg/m3.