Departments have found uses for heavy rescues that move the units beyond simple toolboxes on wheels. Today's heavy rescues are more like full shops on wheels equipped with a variety of built-in components that can light, lift, pry, pull, saw and stabilize to assist rescue personnel in many different situations.

Many departments run heavy-rescue units because they have to respond to a wider range of complex rescue situations. Urban search-and-rescue operations are a good example. Earthquakes, floods, hurricanes and tornadoes can cause widespread structural damage and require extensive rescue efforts to remove debris and locate victims. Depending on the situation, these operations may extend over a long period and require many types of equipment. Rescue workers often need to shore up structures to prevent further collapse, cut away portions to gain access and raise other portions to free victims. To do this, they need electrical, hydraulic, pneumatic and mechanical power for tools, as well as lighting, ventilation and breathing air to provide a safe work environment.

Trench rescues, tunnel rescues, heavy machinery rescues and many other emergency situations require a similar amount of specialized tools and equipment. To carry it all, many departments now are specifying heavy-rescue units with lots of built-in components.

One key component found on almost all heavy rescues today is a large-capacity electrical generator. Most units have generators with 20- to 40kw output, and some have even higher. In addition to providing power for lights, these big generators also are used to run a variety of built-in and portable equipment.

One popular use for electrical power is a built-in hydraulic unit to power rescue tools through hose reels. Building the power unit into the apparatus and running it off the generator, instead of using a portable engine-driven unit, allows the rescue tools to be put into operation faster and minimizes the noise at the point of extrication. It also allows a single power unit to run two or more separate rescue tools to further speed operations.

Other uses for electrical power on heavy rescues include electric winches to lift and pull heavy objects, breathing-air compressors to refill SCBA cylinders and utility air compressors to power pneumatic tools for use where electrical tools wouldn't be appropriate. Some urban search-and-rescue units are equipped with radial-arm saws to quickly cut lumber in required lengths and shapes for cribbing and shoring.

Another key component on many heavy rescues is additional space to carry supplies and equipment and specialized compartment designs to handle large or irregular-shaped items. In addition to all the handheld tools, many rescues carry stabilizer struts to steady overturned vehicles, inflatable lifting bags to raise large objects and collapsible tripods to provide lifting points for confined-space rescues. Trench rescues require plywood sheets for shoring and tubular spreaders and struts to stabilize trench walls. Urban search-and-rescue operations require large amounts of structural lumber to build cribbing. All of these items require custom body designs with large compartments. To safely store and remove very heavy items, departments often specify roll-out drawers or trays with capacities up to 1,000 pounds. Roof compartments are popular for very long items, and transverse compartments are useful for storing oddly shaped items.

The need for more space has led some departments to specify tractor-trailer rescue units. This configuration has better weight distribution and maneuverability than long straight-frame trucks, and the trailer can be designed with a dropped center frame height to provide additional compartment space and lower compartment floor heights.

Some departments have taken the heavy-rescue concept one step further by including a variety of equipment to gain credit on their Insurance Services Office rating. In some cases, it may give them enough extra credit to boost their rating to the next highest classification.

The ISO Fire Suppression Rating Schedule assigns points for engine companies, ladder companies and service companies. Service companies are used to carry equipment for forcible entry, ventilation, overhaul and salvage at structure fires. This equipment may be carried on a designated service company apparatus, or it may be carried on a rescue unit or other apparatus that automatically responds to all structure fires. Many departments assign the service company equipment to a ladder unit, but those departments that don't have a ladder can still gain points by placing the service company equipment on a rescue unit.

The required equipment includes specific types and quantities of SCBA, spare SCBA cylinders, salvage covers, pike poles, a generator, lights, a smoke ejector, an oxyacetylene cutting unit, a power saw and other equipment. ISO will allow departments to substitute certain items for those on the list. For example, it will give credit for a hydraulic or pneumatic cutting tool in place of the oxyacetylene cutting unit, and a positive-pressure fan in place of a smoke ejector. Many of these items are already part of a rescue unit's equipment, and departments simply need to document them and ensure that the rescue is dispatched to every structure fire to gain credit.