Mgt 104a Carbon in Respirators

[michael edward badolato jr]

Also see Mgt 104 Respirators: Particles and Adsorbed Hydrocarbons

A charcoal cartridge is not a universal filter - each cartridge contains charcoal for specific gases - for example activated charcoal without further treatment or impregnation works by physical adsorption only and may be used for organic vapor (Calgon Carbon). To be effective for other gases charcoal is variously treated in the realm of proprietary secret.

Haycarb.com:

"...The highly developed micropore structure of our activated carbon and controlled chemical impregnation process conditions ensure the uniform adsorption of gases by the internal surface of the pore structure and maximize adsorption capacity..."

Most of the exposure is not gas - but instead condensed liquid phase components adsorbed (distinct from absorbed) onto fine particle  cores - submicron up to about 10 microns. The particles act like vector placing the hardened liquid phase components in the tissue. Immediately there is a large release of the adsorbed chemical off the particles - but bonding energies involved in the initial adsorption have the desorption in 2 phases: the other half to be gradually released over months and years (Gerde 2001, 1997). 

In contrast, gases have a short residence time and are a less dense phase - smaller amount of the exposure.

Charcoal removes some of the gases - doesn't filter the particles and adsorbed liquid components - and may produce an emission adding to the exposure. The suspension of particles with adsorbed components along with the gases present is referred to as an aerosol.

The only time a charcoal cartridge makes sense is in a concentrated gas exposure for which the charcoal is designed.

Trying a respirator with charcoal for nuisance level OV and another for acid gas - each time the charcoal added toxicity - was apparently far worse than without charcoal.

The first comparison was a 3M N95 with and without charcoal - and the second was a the Moldex 2300N95 without added charcoal and Moldex 2500N95 which has charcoal.

Apparently either the charcoal forms a "sink" (adsorption) - accumulated toxicants are pulled out of the charcoal while breathing (desorption) - or the charcoal itself degrades and emits at a fine level that is not visible.

Since the bulk of exposure is chemical adsorbed onto fine particles it makes sense to stick with the N95 disposable particulate respirator without charcoal - the PM filtration may be the best possible for reducing exposure while avoiding toxicity presented by the use of charcoal.

N95 designates 95% or more filtration of NACL aerosol larger than .3 microns. Since the greater amount of chemical is on the larger particles - the effectiveness may be far greater than 95%. However, an MCS person will still feel effected by pollution since the relatively slight amount that gets by is enough for a reaction.

As mentioned above, carbon might only be a good idea for a specific high intensity gas or fumes for which the carbon is designed - and the respirator removed after the exposure.

Mgt 104 Respirators: Particles and Adsorbed Hydrocarbons

References

Calgon Carbon

Haycarb.com

Gerde P. et al. The rapid alveolar absorption of diesel-soot adsorbed benzo[a]pyrene: bioavailability, metabolism, and dosimetry of an inhaled particle-borne carcinogen. Carcinogenesis 22;5:741-49 2001

Gerde P. et al. Benzo{a}pyrene at an environmentally relevant dose is slowly absorbed by, and extensively metabolized in, tracheal epithelium. Carcinogenesis 18:1825-32 1997