OSHA Hazard Information Bulletins
Suffocation Hazards in Flat Storage Buildings and Tanks
December 15, 1994
- JOHN B. MILES
- DIRECTORATE OF COMPLIANCE PROGRAMS
- Hazard Information Bulletin - Suffocation Hazards in Flat Storage Buildings and Tanks
The purpose of this Hazard Information Bulletin is to heighten awareness of the existence of a serious engulfment (suffocation) hazard in grain handling facilities. Additionally, this bulletin is intended to alert OSHA's field compliance personnel to such hazards so that the inspection scope in similar facilities can be expanded to address them.
A serious hazard was reported by the Jacksonville, Florida, Area Office associated with the cleaning of a large flat bottom grain tank located at some feed mills or other grain storage facilities. In October 1993, while "walking" the corn during the cleaning of a tank at a feed mill which services a Florida poultry processing plant, an employee sank into the corn, was engulfed and suffocated. These tanks are generally designed with a single discharge auger that collects and transports grain from the silo to another destination (the feed mill). In the process of moving the grain from the tank, a residue will be left behind and some will extend upwards along the side of the tank. This grain frequently cakes together and must periodically be moved down to the auger for discharge.
In the Florida case, workers entered the tank from a side access portal several feet above the floor. While the auger was operating, they walked around on the corn (knocking it down from the sides of the tank with picks and poles and pushing it with their feet), causing it to move toward the center where it was removed by the auger.
A cleaning process similar to that used in Florida is likely to be necessary in other storage facilities as well. Workers who enter the tank to clear the grain may be required to "walk" a sizable accumulation of grain. If the depth of the grain is more than a few feet and, particularly, if the discharge auger is running while the workers are in the tank, the employees are exposed to the hazard of suffocation, if the grain shifts and engulfs them. This hazard is recognized in the industry and is addressed in the preamble to the grain handling standard, 29 CFR 1910.272.
Hazards in grain storage structures used in agricultural operations covered by 29 C.F.R. Part 1928 shall be cited under the General Duty Clause. Grain storage structures used in non-agricultural operations shall generally be cited under the grain handling standard, 29 C.F.R. 1910.272. The requirements of 1910.272, however, do not cover structures if the diameter of the structure is greater then the height, unless entry is made from the top of the structure. This lack of coverage was based on comments received during the rulemaking that certain flat storage structures do not present engulfment hazards.
Because engulfment and mechanical hazards may exist in a grain storage structure with a diameter greater than its height and not entered from its top, such a structure can be cited under the Permit-Required Confined Space and Lock-out/Tag-out Standards (1910.146 and .147).
To reduce or prevent suffocation and mechanical hazards in these structures, the following guidance is provided:
- Employers must have written confined space entry and lockout procedures;
- A procedure for clearing the storage tank without exposure to employees to an engulfment hazard must be developed and implemented;
- Or, if the job cannot be done without employee exposure, employees must wear a harness with a life line for any entry into any tank or structure where an engulfment hazard is present. The life line shall be of such length that it would not allow the employees to sink any further than waist deep in the grain;
- Employers could use an alternative protective system, e.g., static line restraint devices in conjunction with the life line and harness;
- An attendant must be stationed outside of the structure where he/she can monitor the employees who are inside;
- During any entry, the discharge auger shall not be running;
- Wherever practicable, the employer should install horizontal sweep augers at floor level that move the grain from the periphery of the structure, where the corn is "bridged" or "hanging on the side" to the center for discharge. This action removes the requirement (other than for maintenance purposes) for employees to enter the structure to move the grain manually.