Equipment used exclusively for conveying and storing plastic and/or rubber solid materials is permitted by rule, provided that no visible emissions occur and all the conditions of this section are met:(1) equipment used for conveying of powders or resins to storage silos must be equipped with fabric filter(s) having a maximum filtering velocity of 4.0 feet per minute (ft/min) with mechanical shaking or 7.0 ft/min with air cleaning; and(2) transfer of powders or resins is accomplished in an enclosed system.