the ideal widfire shelter
shelter in place or evacuate?
How to plan and execute the ideal wildfire shelter.
The key factors for the planning and building a wildfire shelter:
- Wildfires can create situations that humans cannot survive (without protection).
- If you cannot evacuate before the fire reaches your position, you will have to shelter in place.
- When large fuel reserves burn, they can create a situation where it is “raining embers.” Brace for impact.
- Removing fuel (trees, bushes, trash, and other materials) around to your home is mandatory.
In this article, we are going to discuss the ideal wildfire shelter. Not everyone has the space or budget to build a shelter like this, but you will understand the principals that will keep you safe when sheltering in place during a wildfire.
A wildfire is a formidable enemy. It has several weapons:
- Heat: excessive thermal energy will burn skin and raise core temperature. Both of these can kill.
- Smoke: besides acute repertory exposure that can kill, there are many carcinogens in smoke. These are compounds that have been determined to cause long term illness. Smoke inhalation is the leading cause of death due to fires.
- Carbon monoxide: this is a deadly byproduct of incomplete combustion. In a wildfire, you will be surrounded by combustion that is very incomplete.
- Oxygen deprivation: in an enclosed space, fire will consume oxygen.
- Dangerous structural damage: both trees and man-made structures like homes and shops can be damaged by fire to the point of falling. Even if you avoid the direct impact, they can block your evacuation, requiring you to shelter in place.
This is why we need to engage in battlespace preparation long before the fire arrives. Remove fuel around your home and consider purchasing or building a wildfire shelter.
Lessons from down under
A redditor from Australia commented on what was learned after their 2007 Black Saturday bushfires (emphasis added):
I haven’t been paying a huge amount of attention to the wildfires in the United States at the moment, but some lessons from the Australian bushfire season crossed my mind and I thought I’d share it here.
In Australia in 2007, the Black Saturday bushfires killed 173 people and burned 1,100,000 acres in a single day. In the 2019-2020 bushfire season, more than 46 million acres burned between September 2019 and March 2020, but only 34 people died (many of them volunteer firefighters). From what I can tell, the major change after Black Saturday was that the old “leave early, or stay and defend your home” strategy employed by people all over the country (and the fire authorities) before 2007 has been replaced by early evacuation for everyone. If you’re in the path of a fire, you leave. You don’t stay to wet down the outside of your house, or huddle inside while the fire passes over before going out to mop up any embers because there won’t be anything left to mop up. A lot of the people who died on Black Saturday had experience defending their homes from bushfires, but the fires were just incredibly fast and incredibly hot, and no amount of experience would have made a difference.
This is a valid point. Property is not usually worth risking your life for. But there are valid reasons that some people need to plan on sheltering in place during a wildfire. Even if you don’t plan on it, you could get trapped with no way to evacuate. A fire that starts at your neighbor’s house may block your immediate evacuation. Fires movement is dependent upon wind speed and direction. They can jump from ridge to ridge and be on top of your home before you have a chance to get out.
Should I stay or should I go?
There are some valid reasons to shelter in place while your neighbors evacuate. They included:
- A significant investment in a home that is defendable, but not having confidence in the local firefighters and law enforcement to defend your home from a fire and/or looters.
- Animals that cannot be easily moved and must be sheltered in place.
- Essential employees that must remain on station to maintain critical infrastructure.
A better argument can be made for evacuating than any of the above reasons. This website is about protecting you and yours. The safest place to be in a natural or man-made disaster is someplace else. If in doubt, bug out.
Fuel for the fire
To have a fire, you must have an ignition source as well as an ongoing supply of fuel, oxygen, and heat.
Ignition sources can include:
- Lightning strikes
- Wind-blown embers
- Malicious people engaged in arson
- Vehicles and power tools
Fuels can include:
- Structures like you home, garage, barns, and sheds
- Biomasses like grass, trees, and bushes
- Accelerants like fuel, oil, and solvents
Any home located in a potential wildfire area needs to have fuel around it reduced or eliminated before fire season. This is foundational and non-negotiable. The fire cannot be reasoned with. It must be starved of fuel or your home will burn. Firefighters often perform triage and determine which homes can be saved by the fuel load on the property. A home with a significant fuel load will eat up resources and most likely burn up in the end. It is not worth saving. If you live in an area with a wildfire season every year, create a fuel-free buffer zone around your home and show some appreciation to anyone who fights fires.
For this reason, the ideal wildfire shelter should be near, but not inside your home or basement. They should be placed for easy access from your where you spend the most time. There are other considerations about where you place your wildfire shelter, from most important to least:
- There must be no fuel near your shelter. This includes your home. If your shelter is too close, it will receive significant thermal energy (heat) that radiates from the burning structure. And, the structure can collapse in the direction of the shelter, putting combusting fuel right on the roof or walls. Imagine your home collapsing toward your shelter. Now locate your shelter outside of where it will land and give it a comfortable margin of safety.
- You must always have a path back to your shelter. This needs to start when you build it. Ensure that there are fuel free paths to all of the critical resources you need to manage: your home, garage, barn, etc. Your shelter should be centrally located to all of the centers of gravity on your property.
- Access to where you turn around and park your vehicles. If you have to evacuate after first taking shelter, you need to be able to access your vehicle. Conversely, if you need to be rescued after taking shelter, your rescuers will need to turn their vehicles around and access your shelter. Just like when there is incoming rounds, you need to move from cover to cover rapidly and without hindrance. The fire requires fuel. No fuel, no hindrance when it’s go time.
- Speed and convenience when loading your shelter up with your valuables. A shelter that is significant distance from your home will require much more effort to relocate your lockboxes, guns, important papers, pets, etc. You will probably be wearing a respirator while performing this relocation. A dedicated wildfire shelter should be planned and constructed with the same care as a panic room. It’s your place of refuge when the world becomes dangerous.
Fire shelters inside homes have their place, but they are not the ideal location for a wildfire shelter.
Up above or down below?
Once you have a location chosen, the next question is whether to put it above or below ground. The question boils down to three issues:
- Are there any trees or structures that can fall on the shelter? Backpackers and bushcrafters call them widowmakers. You can build a shelter to resist the effects of trees or branches falling on it, but these hazards also bring fuel to your shelter when they fall. Your shelter needs to be (and stay) a fuel free zone.
- Are there any subterranean difficulties like a high water table or shallow bedrock? Again, this is something that can be overcome with the right shelter design, but it’s going to cost more time and money.
- Are you in an area that gets extremely hot during fire season? If so, below ground has the advantage of insulation against the heat of the sun as well as the heat of a wildfire.
The below ground option
A wildfire shelter below (or at) the surface has some significant advantages:
- Falling trees and branches have a significantly harder time causing structural damage to the shelter with their kinetic energy. And the burning fuel they bring to your shelter is less likely to transfer heat inside the shelter with the insulation of packed earth around and/or over it.
- Your shelter will remain cooler throughout fire season. You don’t want the only safe place from a wildfire to feel like a sauna when you open the door.
Unlike a bomb shelter, an underground wildfire shelter can be at grade and covered with a concrete pad. In other words, the top of the shelter will be even with the ground. The shelter should have enough structure to hold the weight of a vehicle. If you decide to bury it deeper and backfill over it, you will have more insulation against heat transfer from burning fuels and the weight of a vehicle will spread out beyond the shelter. Unless you live in an active geothermal zone, the earth is the best heat sink in the world.
Prefabricated steel bomb shelters are a very good option for subterranean wildfire shelters. They are made to be buried and most of them come fully equipped with an NBC air filtration system. Be sure and see the article on NBC air filtration systems for complete understanding of the best air filtration systems for wildfire smoke. A small underground shelter that does not need to be buried very deep can be installed with a backhoe. This will save time and money over using a large excavator to excavate the hole and lift the shelter into place.
The above ground option
Above ground, a concrete shelter makes more sense. Either formed and poured concrete or block walls on a concrete pad with a concrete top. The problem with above ground steel shelters is that they have a high level of heat transference from fires outside to the inside of the shelter. Eight inches (203 mm) of concrete will conduct heat to the inside, but not nearly as fast as a quarter inch (6.35 mm) of steel. Even if they are insulated, steel boxes become ovens in the hot sun or a wildfire. Insulation acts to slow heat transference, it does not stop it. It’s a speed bump that works both directions.
Outfitting your wildfire shelter
There are specific components that are required to weather a wildfire. You have options with these components, but you must be insulated from the heat and have filtered air to breath.
The door must be non-flammable. It should be insulated, but if you have removed all of the fuel from around your shelter, a steel fire door without insulation (20 minute fire rating) will suffice. The best solution is an insulated 90 minute fire rated door like the one linked directly below. You should consider mounting it as an inward swinging door. Since this is not a bomb shelter, the door does not have to hold a significant load. The force of a nearby detonation usually requires an outward swinging door to transfer the blast load directly to the frame, instead of through the hinges and latches. Inward swinging doors are almost immune to trapping the occupants inside due to debris on the outside.
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At Amazon: Commercial steel fire rated entry door (36″x 84″)
The second way out
If you’ve read the article on bomb shelter plans, you know we’ve hammered home the importance of an emergency egress portal that is separate from your main door. Every point made in that article about not getting trapped in your bomb shelter also applies to wildfire shelters. A second door on an adjacent wall or a hatch on the roof is recommended. We want the second way out to be on a different plane than the first so that if debris is force up against one side or the top of your shelter, you still have a way out. You must make it out.
The air filtration and ventilation system
The best air filter for wildfire smoke is a Nuclear, Biological, and Chemical (NBC) air filtration system. These are specialized wide spectrum air filters that filter out both particulates and gases. Smoke has both. If you are just filtering particulates, you can still smell the smoke and are being exposed to a number of carcinogenic compounds. See the article on NBC air filtration systems for a complete breakdown of these filtration systems that includes recommendations and protocols.
The backup air filtration system
An essential part of the shelter air filtration system is respirators for all of the occupants. This provides a backup and will definitely be needed for time outside the shelter both before and after the fire impacts your location. 3M recommends that to use an organic vapor cartridge with the addition of the particulate filter.
- 3M rugged comfort quick latch half facepiece Respirator 6503QL
- 3M particulate filter 6055 A2 for gas and vapour, 2 pairs
- 3M respirator filter retainer 501, 2 each set
- 3M 5925 P2 R particulate filter P2R, 2 pairs
- 3M Ultimate FX full facepiece respirator FF-402
These are a half mask respirator, the recommended filter cartridges, and a full mask respirator.
The sprinkler system
Above ground shelter should have a sprinkler system on the outside to provide additional fire resistance. It will raise the humidity around your shelter and dampen the outside roof and walls. Humans are conditioned to view water as the antidote to fire. As long as you have water pressure, a properly designed and installed sprinkler system will at least provide a mental “barrier” to the fire. At most, it might save your life.
Pressurize water is a valuable resource that can be interrupted during a wildfire. A water system like a well with a pressure tank requires power to produce water pressure. They usually pressurize less than 80 gallons at a time, which is not much if you are feeding a sprinkler system or fighting a wildfire. If you are on a municipal water system, it still takes electricity to purify and pump the water up to the large holding tanks. But there are many other homes that will be drawing from those tanks. Either way, your water pressure can disappear. But it might not, so a sprinkler system is a worthwhile investment.
The ideal sprinkler system will throw water on each wall and the roof of your shelter. One solution is to use the soft tubing and sprinklers that are used in greenhouses. They usually come in either drip or mist irrigation. The mist irrigation is preferred. A halo of water mist around your wildfire shelter can be very comforting. The only issue with these systems is that they have small diameter hoses and you may need more than one to deliver enough water to dampen your shelter. But, they are an inexpensive solution to the problem. You should also install an inline water filter before this system so the small water ports do not get clogged with particulates. There are also kits that mount a sprinkler head in an insert that mounts in your gutters. These are a convenient way to get water onto your roof. A water meter on the main line to your sprinkler system will let you know how many gallons a minute will be used.
- Outdoor misting cooling system – automatic plant watering system
- DAE AS200U-75 water meter gauge, 3/4″ NPT couplings, measuring in gallons
- P3 save a drop water flow meter – measure gallon usage from a garden hose
A greenhouse watering system and two styles of inline water flow meters.
What to store in your wildfire shelter
These items should be in your shelter 100% of the time. They should be checked annually, at the start of the wildfire season.
- A fire extinguisher (two is better, one by each door/hatch).
- A smoke and carbon monoxide detector.
- Full face respirators for each person.
- A carbon dioxide detector.
- Long term storage food and water.
- A deep cycle battery on a trickle charger with 12 volt lights and USB ports.
- Cell phone chargers.
- An AM/FM/WEATHER radio with extra batteries.
- Flashlights and extra batteries to back up the 12 volt lights.
- A first aid kit.
Be sure to store them properly. Moisture is the enemy of most things in an enclosed space like a shelter.
- Amerex B500, 5lb class A,B,C dry chemical fire extinguisher (2 pack)
- Carbon dioxide/temperature/humidity air quality monitor
- First Alert smoke detector and carbon monoxide detector alarm
- KKmoon oxygen concentration meter with sound-light alarm
- Corentium Home Radon Detector by Airthings
These are the recommended life support instruments for shelters.
The protocols for using a wildfire shelter
When you are first alerted to the presence of a wildfire that could impact your location, these are the steps to take. Wildfires can move at up to six miles per hour. This means that a fire that is 10 miles (16 km) miles away can be at your home in less than two hours. Under the right conditions, fires can jump from ridge to ridge. A wildfire 10 miles away is a clear and present danger to your life and home.
The US Forest Service lists three levels of evacuation warnings:
- LEVEL 1 EVACUATION or PROTECTION ALERT: A wildfire threat is in your area. It would be wise to consider planning and/or packing, in the event an evacuation becomes necessary.
- LEVEL 2 EVACUATION WARNING or NOTICE: High probability of a need to evacuate. You should prepare now by packing necessary items and preparing your family, pets, and vehicle for potential departure.
- LEVEL 3 EVACUATION REQUEST or ORDER: Occupants of the affected area(s) are asked to leave within a specified time period, by pre-designated route(s). Perimeter roadblocks are typically established.
Most jurisdictions have similar levels. Level 3 notices are given as either mandatory or highly recommended with the understanding that emergency services will not be responding if you choose to shelter in place and not evacuate.
If you are under a mandatory evacuation order, you need to leave. The protocols below are only for when you are trapped. If you do not evacuate, you still should have vehicles in good working order fueled up and ready to roll.
Level one (ALERT) protocols
This is the time to check out your shelter:
- Unlock the door to your shelter and inspect it inside and out. Ensure the stores you left in there are intact.
- Test the filtration and ventilation system. Check the ventilation pipes for obstructions. The most common obstruction is insect nests. Also check your respirators at this time. Your air supply comes first.
- Put the items the list below in your shelter.
- Establish a line of communication with your neighbors. Make sure they know the evacuation notice.
You do not have to wait until you are on an official level 1. If a fire lands on your radar, then act.
Level one (ALERT) shelter stores
These items should be secured in your wildfire shelter when you are at evacuation level one:
- Keys to your vehicles in case you decide to evacuate at some point.
- Fresh food and water.
- Your valuables: cash, jewelry, and guns (don’t forget the ammunition).
- Your important papers: start with the deed to your home and the declarations page from your homeowners insurance, then move on to the video you have stored of your home’s contents so you can document what was lost. Also include your most current bills: property taxes, electrical service, water, sewer, etc.
- Your memories: pictures, videos, and heirlooms.
- Critical medicine, CPAP machine, etc.
Include anything else of value you have. Your wildfire shelter is a time capsule. Whatever you put in it will be there in the future.
Level two (NOTICE) protocols
Level two is all about having everything set so you can immediately enter your shelter.
- Have your respirator on your person or close at hand.
- If you have water pressure and plenty of water, start the sprinklers on your shelter and start dampening the likely avenues of approach the fire may take to reach your home.
- Get your animals ready to weather the firestorm. Field animals should be corralled into areas with little or no fuel. House pets should be in the shelter or in one room of your home so you do not have to find or catch them.
- Start your vehicles and check the gauges for fuel and oil. Either leave the keys in the ignition or put them in your pocket and notify everyone where they are at.
Level two is your last chance before your position could be overrun by the fire to check everything. Make your time count.
Level three (EVACUATE)
This is the time to commit. You need to do one (and only one) of the following:
- Get everything you value inside your shelter and STAY THERE. Repeat: DO NOT LEAVE YOUR SHELTER.
- Lock your home and evacuate immediately. GET TO A SAFE PLACE WHERE THE FIRE CANNOT REACH YOU.
Again, you need to commit to evacuating or sheltering in place. The worst place to be is in between evacuating or sheltering. Move decisively.
Other uses for a shelter
Another thing to consider is all of the functions that a shelter can provide. This list is from the article on Safe Room Location:
- A bomb shelter to protect from nearby detonations.
- A fallout shelter to protect from radioactive fallout.
- A panic room to protect from malicious people.
- A vault to protect valuables from burglaries.
- A secure onsite data repository to protect from data loss.
- A storm shelter to protect from severe weather and geological events.
- A fire shelter to protect from wildfires or structural fires.
- A secure rally point for family members if you need to evacuate the area.
If you are building or purchasing a multi-use shelter, there will be other considerations besides wildfires. This website is an ongoing discussion of these considerations in the articles.
Fires can wipe away everything you have devoted your life to, but they are not worth your life. When deciding between evacuating and sheltering in place, always remember the term “raining embers.” The best defense is preparation. Remove fuel, build a shelter, follow the protocols, and stay safe!
Next article: The ideal panic room
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