As far as chemicals on a farm, there can be a wide variety, from anhydrous ammonia to diesel fuel to gasoline to pesticides and herbicides, to name a few. Never try to pull someone out of a grain bin that is buried, even if they are buried only waist deep. You may pull the trapped person apart before you free them. Never turn on the auger thinking the grain will run away from the trapped person. It will just pull them down into the grain further.
Most times digging around the victim, then shoring with plywood is more effective.
In some instances, the grain bin must be cut from the outside to empty the bin, but great care must be taken in performing this. If the cuts are made in the wrong place, the grain bin may collapse. You also need to be aware of fire and spark hazards when there is grain dust in the air. If your department has air bags, get familiar with them and know their limitations. Always remember when you lift, to crib.