Dusts electrically active

Qass I consists of electrically active dust for which, when precipitated, the adhesive forces are greater than the autohesive forces, so that there is no aggregation of particles. Such dusts include roasted zinc silicate and zinc oxide, finished cement, converter soot, zinc oxide, corn starch, ball clay, and diatomaceous earth after hot caustic treatment. 

Qass II consists of electrically active dusts that lose their charge upon adhesion and may form strong aggregates. These include stack effluents of the zinc oxide type, raw cement, discharges from nickel smelting furnaces, magnesites, chromium ore, wheat starch, powdered sugar, and molybdenum oxide. 

In the following tabulation we list the conditions for adherence and nonadherence of electrically active dusts in Classes I and II ... 

The classification of dusts on the basis of electrical activity and conditions of adhesion to charged surfaces has been discussed previously (see Section 36). 

Dust-tight electrical systems should be used in areas where activated carbon is present, particularly powdered products (66). When partially wet activated carbon comes into contact with unprotected metal, galvanic currents can be set up these result in metal corrosion (67). 

R.H. Essenhigh, Pennsylvania-StateUniv.MinerallndsExptlSta, Cite No 64, pp 1-6(1963) (An appraisal of dust explosion research) "Activities of the Instrument Society of America Subcommittee on Electrical-Dust Hazards , by T.W. Moodie, Ibid 27-32 "Proposals for Experiments on Dust Explosions by P. Lafitte R. Delbourgo, Ibid, 19-21. 

The most likely exposure to picric acid is in the workplace from use in explosives, matches, electric batteries, from etching copper, and making colored glass. These activities could lead to dermal contact or the inhalation of dust of picric acid or its salts. 

Many types of activated carbon have high electrical conductivity therefore, dustproof motors and enclosed switches should be installed in rooms where carbon dust is present. 

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