I wanted to follow up on this with some actual documentation opposed to anecdotal evidence.
Here's a link to the CDC manual on RCFs (Refractory Ceramic Fibers):
https://www.cdc.gov/niosh/docs/2006-123/
and a few excerpts from the CDC criteria that I feel are worth noting:
- According to Table 2-1 the diameter of post-production RCFs is 1.2 μm – 3 μm. Cheng et al. [1992] analyzed an air sample for fibers during removal of after-service RCF: (RCF that has been subjected to greater than 1,800 F (~1,000 C) and has partially converted to the silica polymorph cristobalite) and found fiber diameters as small as 0.5 μm (Pg 15-16).
- Longer and thicker (>3.5 μm in diameter) fibers are preferentially deposited in the upper airways. . . and are generally cleared via the mucociliary escalator (blowing your nose and coughing up phlegm). Thinner fibers tend to maneuver past airway bifurcations into smaller and smaller airways - (Pg 91)
- NIOSH concludes that RCFs are a potential occupational carcinogen. Furthermore, the evidence of pleural plaques . . .observed in persons with occupational exposures to airborne RCFs is clinically similar to that observed in asbestos-exposed persons after the initial years of their occupational asbestos exposures – (Pg 108)
- NIOSH concludes that on a continuum of fiber toxicity, RCFs relate more closely to asbestos than to fibrous glass and other SVFs and should be handled accordingly. – (Pg 111)
- increased exposures to airborne fibers have been linked to pleural plaques, small radiographic parenchymal opacities, decreased pulmonary function, respiratory symptoms and conditions (pleurisy, dyspnea, cough), and skin and eye irritation. Many of the respiratory effects showed a statistically significant association with RCF exposure after controlling or adjusting for potential confounders, including cigarette smoking and exposure to nonfibrous dust. – (Pg 89)
- the RCFC (Refractory Ceramic Fibers Coalition) recommends that workers wear respirators whenever the workplace fiber concentration is unknown – (Pg 96)
■ At a minimum, use a half-mask, air purifying respirator equipped with a 100 series particulate filter (this respirator has an assigned protection factor (APF) of 10 – (Pg 119)
- Respirators should not be used as the primary means of controlling worker exposures. Instead, NIOSH recommends using other exposure-reduction methods, such as product substitution, engineering controls, and changes in work practices. – (Pg 118)
I read the last point above to suggest that coating the RCF with castable refractory (would that be a change in work practice or engineering control?) is better than relying on a respirator to protect yourself.
Stay safe and have fun.
