The Housekeeping Strategy
The other school of thought about grain elevator safety is enamored of—some say preoccupied with—"housekeeping" (or dust control). The label can be misleading to the extent that it conjures up only images of brooms and vacuum cleaners. Dust control is aimed at both airborne and layered dust. Airborne dust can be removed by various systems of aspiration, also called pneumatic ("moved or worked by air pressure)" dust control. Pneumatic dust-control systems have four major components: hoods or other enclosures; ductwork; a filter, or dust collector; and an exhaust fan. Layered dust can also be removed automatically, but in all but the largest facilities it is removed manually: with vacuum cleaners, brooms, compressed air, and, in some cases, water.
Both types of housekeeping (pneumatic dust control and layered dust removal) are controversial, but in the first case the disagreement is mostly technical, while in the second it is largely a matter of economics. The technical potential of pneumatic dust control is highly disputed. One grain elevator insurance company touts a system it claims can reduce dust concentrations in the bucket elevator below the lower explosive limit. The technology was not proven to the satisfaction of a 1982 NAS panel, but panel members placed a high priority on continued research in this area. Many in the industry still consider such technology unavailable. Others claim to have used it successfully. Both are probably right, as the design of pneumatic dust-control systems is, according to a Cargill engineer, "more of an art than a science." Engineers cannot simply take specifications for the desired concentration of airborne dust (or rate of accumulation for layered dust) and design a system that will perform accordingly. The technology for removing airborne dust is too uncertain. Much depends on how the system is installed and maintained.
Layered dust poses much less of a technical problem. How to remove it effectively is not very controversial (although the virtues of vacuuming versus sweeping are a minor topic of disagreement). For large facilities, dust removal is usually part of normal operations. Sweeping is done at least once per shift at all export facilities. But for many smaller facilities, removing layered dust means hiring additional labor and slowing down operations when they are most profitable. Few quarrel
with the conclusion of the NAS that housekeeping and maintenance are often given low priority and are usually the first tasks postponed when there is a rush of business. A grain company representative on the NFPA Technical Committee on Agricultural Dusts concurs that "there are many, many filthy ones that get by." A less tactful USDA investigator describes the prevailing levels of housekeeping in grain elevators as "fair to abysmal." The main objections to stricter housekeeping rules is the cost. The controversy, in short, is managerial, not technical.
Trying to estimate the number of "bad apples" is difficult, however. "It depends on which day of the week you are counting," as one industry representative put it. There has been very little counting to date. No one even knows with precision how many elevators there are, let alone when they were all built and what kind of equipment they currently use. Harder still is determining the relative cleanliness or safety levels of grain-handling facilities. No industry group investigates or collects information on explosions. NFPA collects statistics through newspaper clippings and voluntary reporting from the fire service, but this information is hardly comprehensive. A USDA task force concluded that the NFPA estimate of annual fires in grain elevators may understate the actual situation by a factor of five.