Electromagnetic pulse events and severe solar storms pose a genuine risk to the electronics we rely on daily. Faraday bags offer a practical, portable layer of defense that fits into any preparedness strategy.
What Is an EMP?
An electromagnetic pulse is a short burst of electromagnetic energy that can occur naturally or be generated by a weapon. The pulse creates a rapidly changing electric and magnetic field capable of inducing high voltages in conductive materials. When these induced voltages exceed the tolerance of semiconductor junctions inside modern electronics, the components fail permanently. There are three primary components to a nuclear EMP: E1, E2, and E3. The E1 component is the fastest and most damaging to personal electronics because it exceeds the clamping speed of standard surge protectors. The E3 component resembles a severe geomagnetic disturbance, affecting long conductors like power lines.
What Is a Solar Storm?
Solar storms, often called coronal mass ejections (CMEs), are massive expulsions of plasma and magnetic field from the Sun’s corona. When a CME impacts Earth’s magnetosphere, it drives geomagnetic storms. These storms induce geomagnetically induced currents (GICs) in the power grid and long conductive infrastructure. While a solar storm does not produce the instantaneous, high-field-strength E1 pulse of a nuclear detonation, the E3-like effect can last for hours or days. The primary threat to unplugged handheld devices comes from the potential for localized voltage spikes if the device is connected to a charging cable or antenna during the event. Historical events like the Carrington Event of 1859 demonstrate the potential scale of disruption.
How Faraday Bags Protect Against EMP and Solar Storms
Faraday bags function as flexible, portable Faraday cages. They rely on conductive materials, typically multiple layers of metallized fabric or metal mesh, to create a conductive enclosure. When an external electromagnetic field strikes the bag, the free electrons in the conductive layer move to cancel the field inside. This principle protects the contents from both the fast E1 pulse and the slower, longer-duration energy from solar storms.
1. Blocking Electromagnetic Fields
The primary mechanism is attenuation. High-quality bags provide 60dB to 80dB of attenuation or higher across a broad frequency range, typically from low MHz up to 40GHz. This level of shielding reduces the field strength inside the bag to a level that cannot damage sensitive microelectronics. The effectiveness depends on the conductivity of the material and the integrity of the seal. A bag with a faulty closure or worn conductive fabric will leak radio frequency energy, compromising the shield.
2. Redirecting Energy Across the Bag Surface
When the electromagnetic wave hits the conductive outer layer, the energy is converted into surface current. This current flows around the exterior of the bag rather than penetrating the interior. For this to work effectively, the conductive layer must be continuous. Overlapping seams, conductive tape, and secure closure mechanisms (like double-fold Velcro or zipper tracks with conductive gaskets) ensure the current path remains unbroken. This surface redirection is why a bag protects against both the rapid rise time of an E1 pulse and the sustained energy of a geomagnetic storm.
3. Providing 360° Shielding
Unlike a hard metal box, a flexible bag must maintain shielding integrity while being folded, carried, or compressed. Quality construction uses a multi-layer laminate: an outer abrasion-resistant fabric, a middle conductive metal layer (often nickel-copper or silver-coated nylon), and an inner non-conductive liner to prevent the stored device from making electrical contact with the shield. Contact between a device’s antenna or circuit board and the conductive layer can create a coupling path that defeats the shielding. The liner also protects the metal layer from corrosion caused by skin oils or moisture.
4. Preventing Cascading Failures
In a widespread event, the power grid and cellular networks will likely be non-functional. A protected phone or radio is useless if its charging source is destroyed. Storing complete functional kits, device, charger, cables, and backup power, inside a single bag ensures the system survives as a unit. This prevents a scenario where the radio works but the battery is dead because the solar controller was fried in a separate location. For more on building resilient power setups, see our guide on off-grid power solutions.
What You Should Store in Faraday Bags for EMP Preparedness
Prioritize devices that provide communication, navigation, information access, and critical utility. Redundancy is key; store backups of primary tools. Ensure all devices are powered off and batteries are at a storage charge level (roughly 40-60%) before sealing.
1. Backup Phones
Keep a deactivated smartphone loaded with offline maps, survival references (medical guides, edible plant databases, manuals), and communication apps that work via mesh networking or Bluetooth peer-to-peer. Remove the SIM card to prevent tracking and reduce attack surface. An older model you no longer use daily is ideal for this role.
2. Two-Way Radios (Walkie-Talkies)
FRS, GMRS, or ham radios allow local coordination when cell towers are down. Store the radios with antennas detached (if removable) and a set of charged batteries. Include a printed frequency card for local repeaters and emergency channels. Consider a dedicated emergency communications plan to define how your group uses these channels.
3. Satellite Communicators
Devices like Garmin inReach or Zoleo units connect to satellite constellations (Iridium, Globalstar) independent of ground infrastructure. They enable two-way text messaging and SOS alerting globally. Store the unit with its charging cable and a mounting clip.
4. Portable Hard Drives & USB Drives
Solid-state drives (SSDs) are more resistant to physical shock than spinning drives, but both are vulnerable to EMP. Store drives containing encrypted backups of identification documents, financial records, medical histories, insurance policies, and technical manuals. Use a USB drive with a metal casing for added physical durability.
5. Solar Charging Power Banks
A rugged power bank with an integrated solar panel or a separate foldable solar panel keeps devices running indefinitely. Store the power bank at storage charge. Include necessary cables (USB-C, Lightning, Micro-USB, barrel connectors for radios) inside the same bag.
6. Medical Electronics (Non-Critical)
Spare continuous glucose monitors (CGMs), insulin pump controllers, or CPAP battery modules can be stored if they are not immediately life-sustaining. Note: Devices required for immediate survival should remain on the person or in a rapidly accessible location, not sealed in a bag that might be buried in gear. Consult your physician regarding backup strategies for critical medical equipment.
7. GPS Units & Navigation Tools
Handheld GPS receivers (Garmin, Magellan) function without cellular data. Pre-load topographic maps and waypoints for bug-out locations, water sources, and rally points. Store with lithium batteries, which have a longer shelf life than alkaline.
8. Flashlight Electronics
High-end regulated flashlights contain driver circuits vulnerable to EMP. Store a backup tactical light or headlamp. Simple mechanical switch lights without digital regulation are more inherently resistant but a protected advanced light offers variable output and signaling features.
9. Drone Controllers and Navigation Devices
If drones are part of your reconnaissance or security plan, the controller, flight tablet, and spare flight controller board for the airframe should be shielded. The drone airframe itself (motors, frame) is generally robust, but the flight controller and ESC (Electronic Speed Controllers) are sensitive.
10. Vehicle Key Fobs
Modern vehicles rely on transponder keys and keyless entry fobs. While the vehicle’s ECU is a larger target, a spare fob in a small bag ensures you can start the vehicle if the primary fob is damaged or lost. This is a low-cost, high-value insurance item.
What NOT to Store in Faraday Bags
- Devices currently in use: A bag only works when sealed. Do not expect protection while a phone is inside but the bag is open.
- Items with active antennas extended: An antenna protruding from the seal acts as a waveguide, piping energy directly into the device.
- Batteries with compromised casings: Swollen or leaking lithium-ion batteries pose a fire hazard inside a sealed conductive bag.
- Large appliances or grid-tied equipment: Faraday bags are for portable electronics. Whole-house protection requires installed surge protection and grounding systems.
- Credit cards or passports solely for RFID protection: While bags block RFID, dedicated RFID sleeves are more convenient for daily carry. Reserve bag space for survival electronics.
How to Build a Reliable EMP Preparedness Kit
Start by auditing your current electronics. Identify the devices that solve your highest-priority problems: communication, navigation, light, and information. Purchase bags sized appropriately; stuffing a bag too full stresses the seams and conductive fabric, creating leak paths. Use multiple smaller bags rather than one massive bag. This compartmentalizes risk, if one seal fails, you do not lose everything.
Label bags clearly with contents and date packed. Inspect seals quarterly for wear, corrosion on conductive threads, or damage to the inner liner. Practice retrieving and deploying the kit. In a high-stress event, fine motor skills degrade; simple double-fold Velcro closures are faster and more reliable than fiddly zippers or drawstrings.
Test your bags periodically. Place a cell phone inside, seal the bag, and call the phone from another line. It should not ring. Test with an FM radio tuned to a strong local station; the signal should drop to static. Note that consumer “RFID blocking” wallets often fail this test because they only block high-frequency RFID, not lower-frequency cellular or radio signals. For a deeper look at testing methodologies, refer to the National Institute of Standards and Technology publications on electromagnetic shielding effectiveness.
Integrate Faraday protection into your broader preparedness layers. A bag protects the tool; your skills and plans determine how effectively you use it. Store bags in multiple locations: a primary kit at home, a grab-bag in your vehicle, and a minimal kit in your everyday carry if feasible. This distributed approach ensures access regardless of where you are when an event occurs.