According to the Mountaineering: The Freedom of the Hills,[3] the ten essentials are:

1.  Map

2.  Compass (optionally supplemented with a GPS receiver)

3.  Sunglasses and sunscreen

4.  Extra food and water

5.  Extra clothes

6.  Headlamp/flashlight

7.  First aid kit

8.  Fire starter

9.  Matches

10. Knife

The textbook recommends supplementing the ten essentials with:

Water treatment device (water filter or chemicals) and water bottles

·  Ice axe for glacier or snowfield travel (if necessary)

·  Repair kit, including duct tape and basic sewing materials.

·  Insect repellent (or clothing designed for this purpose)

·  Signaling devices, such as a whistle, cell phone, two-way radio, satellite phone, unbreakable signal mirror or flare.

·  Plastic tarp and rope for expedient field shelter.

·  A map and compass assists one in not getting lost in the field. Losing one's bearing in unfamiliar terrain raises the risk of anxiety and panic, and hence, physical injury. Maps that cover the relevant area in sufficient detail and dimension (topography, trails, roads, campsites, towns, etc.) and the skill and knowledge to use them are indispensable when traveling through the outdoors, especially when the place of travel lacks signage, markings or guides. Even a basic compass alone can help an individual find his way to safety, by allowing him to maintain a consistent direction of travel. GPS receivers are excellent, however, like any electronic device they can fail and should not be relied upon as the sole means of navigation.

·  Flashlights and headlamps protect against physical injury when traveling in the dark. A flashlight is also useful for finding things in the pack, observing wildlife in dark crevices and folds, and for distant signaling. Extra batteries and bulbs are highly recommended. Lamps using LEDs have become very popular, due to their robustness and low power consumption.

·  Extra food and water can prevent or cure hypothermia and dehydration, common illness that can be serious risks in the backcountry where immediate medical response is not possible. These items also minimize the likelihood of panic. It is not recommended that one eats food when there is no water, as the body requires water to metabolize food.

·  Extra clothes protect against hypothermia. Multiple layers of clothes are generally warmer than a single thick garment. By having the ability to simply take off a layer of clothes, one can avoid overheating, which can cause sweat and dampen clothing. Moreover, a change into dry clothes is the fastest way to become warm. Extra clothing is also useful for protection from the elements, including thorns, insects, sun, wind, and often cold. If necessary, they can be cut into bandages, used as a tree climbing aid, made into hotpads, pillows, towels, or makeshift ropes. For overnight trekking, one should keep one set of clothes dry for wear in the evening. One can wear the "day" clothes during the next day's hike when they are drier.

·  Sunglasses help prevent snowblindness. Sunlight, especially when reflected in snow, can seriously limit visibility, and jeopardize one's ability to travel safely. Sunglasses also help prevent any possible eye injury inflicted by tree branches, flying debris, and other possible hazards while traveling on foot.

·  A first aid kit usually contains items to treat cuts, abrasions (blisters), punctures and burns. Additional items might address broken fingers, limbs, cardiac conditions, hypothermia, frostbite, hyperthermia, hypoxia, insect and snake bites, allergic reactions, burns and other wounds. If applicable, include any personal medications.

A multi-tool

·  A knife is useful for opening packages, building shelter, shaving wood for tinder, eating, field surgery (after sterilization), cutting rope and clothing, etc. A multi-tool such as a Leatherman or Swiss Army Knife is also a versatile choice. A larger knife (machete) might be essential when one needs or desires to go off trail into thicker growth. A heavier axe or knife is more effective when one has larger needs for construction or for collecting firewood.

·  Matches (or a lighter) and fire starter (typically chemical heat tabs, canned heat, or magnesium stick)[4] to light a campfire is useful for preventing hypothermia and to signal for aid. In an emergency, a fire increases one's psychological will to survive.

·  A water treatment device (filter or chemical treatment) makes water potable. In many environments, water, including that from streams, lakes, or pools, needs to be treated for bacteria and viruses in order to ensure safety. Most backcountry travelers carry a water filter: low end models are inexpensive and provide protection against many pathogens, but not viruses. Some more expensive filters and improved chemical treatments get rid of most health risks, including giardia and other protozoa and viruses. Treating the water reduces the likelihood of gastrointestinal diseases. Since some chemical treatments such as iodine or chlorine may leave a bad taste, many suggest mixing in a flavor to hide the taste. These include powdered lemonade or fruit drinks, Tang, Gatorade, or Crystal Light.

·  A whistle is a compact, lightweight, and inexpensive way to signal for help. Although a person cannot shout for a long period, he can whistle for extended amounts of time. Moreover, the sharp sound of a whistle travels over longer distances than the human voice, and provides a much more distinct sound. Although environmental factors such as wind, snow, and heavy rain may drown out a voice, the sound of a whistle is clearly distinguishable in the field.

[edit] Other "essentials"

Other outdoor organizations have variations of the Ten Essentials pertinent to local conditions. For example, Utah's Wasatch Mountain Club lists extra water in place of food, as Utah is mostly desert terrain, and water is more difficult to find [5].

A trowel can be used to dig a cathole.

The Spokane Mountaineers list "thirteen essentials," which supplement the list with emergency shelter such as a space blanket, signaling device, and toilet paper and trowel (for sanitary disposal of human waste. The toilet paper also doubles as tinder for starting a fire).[6]

The "Ten Essential Groups" is an alternative approach to essential gear selection. Items from each group should be chosen depending on the season, geographic location, and trip duration.[7]

The Ten Essential Groups

An Updated Approach to Outdoor Safety by John Shannon

The ten essentials have a history as far back as the 1930's and were created by The Mountaineers, a Seattle-based outdoor organization. After new climbing students often showed up for a climb with inadequate gear, a list of essential items became necessary to require on trips. The original list included matches, fire starter, map, compass, flashlight (extra batteries and bulb), extra food, extra clothing, sunglasses, first aid kit, and pocket knife. Over the decades this list has undoubtedly saved lives. The problem with a single list of ten items is that any given trip may need more than ten items for safety or comfort. Nearly every ten essentials list seen today has ten items and then a few more.
In my weekly reading from backpacking and preparedness websites, the thought of making a list combining ideas from both of those groups came about. That list has turned out to be the "Ten Essential Groups" listed below. It is a grouped listing of items for review to determine what is best for a particular outing. For example, a backpacking trip to Arkansas in March might have one set of essentials, but a snowshoe trip to Taos in February will have additional essential items. Some items in the groups have multiple uses, and some items such as a map and compass should never be left out of your gearlist. Other trips (paddling, caving, biking or canyoneering) will have more items in the tools group specific to that sport. Gaining outdoor skills knowledge by taking a class specific to your chosen sport is recommended. In the worst case scenario, having the gear to remain dry, warm and hydrated until rescued is the goal.

Sierra Club Info

The Ten Essential Groups:

Medical - ID/medical tag, first aid kit, medications, insect repellant
In addition to the usual first aid kit contents, identification with pertinent medical information is good to have along. That information should include your next-of-kin's phone number, allergies, major diseases such as diabetes or hypertension, etc. Some people even carry an "ABC Kit" (Airway, Breathing, Circulation), an emergency kit stored in an accessible location (not in the bottom of your pack) that includes gloves, a pressure bandage, a mouth protector (for CPR), instructions on pressure points and rescue breathing, a Ziploc bag for biohazard materials, an accident report form, etc. Seconds may count in emergency situations.
Shelter - raingear, garbage bags, emergency blanket, bivy sack, tarp, tent, rope
A shelter from the elements might range anywhere from garbage bags to rain gear to a tent depending on the day hike or overnight outing.
Fire - matches, lighter, sparker/tinder, Fresnel lens, stove/fuel
Many preparedness websites recommend having three ways to start a fire. Even though fires are not permitted on most Sierra Club trips except in an emergency, fire making skills are essential to learn.
Hydration - water container, purification method
The importance of staying hydrated cannot be emphasized enough both for the enjoyment of an outing and for survival in the event of an accident or emergency.
Communication - safety plan, whistle, pen/pencil and paper, signal mirror, cellular phone, satellite phone, HAM radio, personal locator beacon
This group contains items that may allow you to, more quickly, get found if lost or rescued if injured. Simply leaving a safety plan with a loved-one will allow Search and Rescue to find you or your group quicker.
Navigation - map, compass, light, altimeter, GPS
Map and compass skills are mandatory. Other items such as a GPS can be a great addition.
Nutrition - extra food, fishing kit
An extra day of food is always a good idea. In a survival situation lasting days, some advocate a fishing kit small enough to fit inside a pill container.
Insulation - jacket, hat, gloves, footwear, foam pad
Proper clothing for the anticipated temperature range is necessary.
Sun Protection - sunscreen, sunglasses, wide-brimmed hat
Protection from ultraviolet rays is needed for the prevention of debilitating sunburn, skin cancer and snow blindness. Sunburn may also make one susceptible to thermoregulation problems as well.
Tools - knife, repair kit, wristwatch, bandana
This group includes miscellaneous items for cutting, repairing gear, and the multipurpose bandana. The listed items may change for other sports.