☣️ UN 3499 • CLASS 9

UN 3499 — Capacitor, electric double layer (with an energy storage capacity greater than 0.3 Wh)

Placard: Miscellaneous. ERG Guide 171. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.

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⚠️ This page is a quick-reference aid. For real incidents: stage upwind, isolate, deny entry, request Hazmat early, and consult the current ERG + SOP/SOG.

UN 3499 At a Glance

UN 3499 (Capacitor, electric double layer (with an energy storage capacity…) is listed as DOT Class 9 Miscellaneous and is assigned to ERG Guide 171. Use this page to review placard data, common hazards, PPE notes, isolation context, first actions, and related UN numbers.

UN 3499 is the transport entry for a capacitor, electric double layer, with an energy storage capacity greater than 0.3 Wh. It is classified as a Class 9 miscellaneous hazardous material and is assigned to ERG Guide 171. For responders, the main concerns are stored electrical energy, damage or short circuit, overheating, casing rupture, fire exposure and possible electrolyte release.

Hazard overview: UN 3499 capacitors are energy-storage devices and may remain electrically charged even when disconnected from equipment. Damage, short circuiting or exposure to significant heat can result in overheating, smoke, rupture or fire. If the casing is damaged, internal electrolyte or other materials may be released. The composition and hazards of the internal electrolyte can vary between products, so responders should obtain the manufacturer's SDS whenever possible.

Response guidance: For a UN 3499 incident, establish incident command, identify the product from shipping papers and package markings, keep personnel away from damaged or overheated units, and approach from a safe position. Treat damaged units as potentially energized until electrical isolation is confirmed. For fire, smoke, leakage or significant damage, use the current ERG Guide 171 together with the manufacturer's SDS and local HazMat SOP/SOG. Do not make assumptions about electrolyte composition or protective clothing requirements without product-specific information when it is available.

UN 3499 Quick Details

UN 3499

Product name: Capacitor, electric double layer (with an energy storage capacity greater than 0.3 Wh)

DOT Class: 9

Placard type: Miscellaneous

ERG Guide: 171 (check current ERG)

Initial isolation: Use the current ERG Guide 171 for initial isolation and protective-action information when responding to a transportation incident. Distances and protective actions must be confirmed from the current ERG and adapted to the actual incident conditions.

Common Hazards of UN 3499

The capacitor stores electrical energy and may remain electrically charged during transport or after equipment shutdown.
Damaged units may present electrical short-circuit, overheating, rupture or fire hazards.
A damaged casing may release electrolyte or other internal materials.
Heating or fire exposure may cause pressure buildup and rupture of the capacitor casing.
Smoke and decomposition products may be hazardous when a capacitor is involved in a fire.
Do not assume that every UN 3499 capacitor has the same electrolyte composition; verify the manufacturer's SDS and product information when available.

Chemical Identity & Physical Properties

Electric double-layer capacitors are high-capacitance energy-storage devices. They generally contain electrodes, a separator, an electrolyte and an external casing with terminals. The exact internal materials and electrolyte formulation vary by manufacturer and model.

Also known as	Electric double-layer capacitorEDLCSupercapacitorUltracapacitorElectrochemical capacitor
Appearance	An electric double-layer capacitor is an energy-storage device that uses electrochemical charge separation rather than the conventional dielectric structure of a traditional capacitor. Commercial units commonly contain electrodes, a separator, an electrolyte and an external casing with electrical terminals.
Flash Point	Not applicable to the assembled capacitor as a whole; electrolyte properties vary by product and should be confirmed from the manufacturer's SDS.
Boiling Point	Not applicable to the assembled capacitor as a whole; electrolyte properties vary by product and should be confirmed from the manufacturer's SDS.
Vapor Density	Not applicable to the intact assembled device; any vapor characteristics depend on the electrolyte or other internal materials released from a damaged unit.
Water Reactivity	The intact assembled capacitor should not be assumed to be water-reactive. If the casing is damaged and electrolyte or internal materials are released, consult the manufacturer's SDS before selecting a cleanup or decontamination method.

Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.

Fireground Response Guidance — UN 3499

Extinguishing Media

For an external fire involving a UN 3499 capacitor, use the extinguishing agent and tactics appropriate for the surrounding materials and the current ERG/SDS guidance. Avoid actions that unnecessarily damage or rupture the capacitor casing.

PPE Requirements

⚠️ PPE should be selected according to the incident conditions, product SDS and department SOP/SOG. Intact units that present no fire, leakage or exposure hazard may require routine protective clothing appropriate to the task. Damaged, leaking, smoking or fire-involved units may require additional respiratory and chemical-protective measures based on the known or suspected electrolyte and fire conditions.

PPE selection depends on the condition of the capacitor and the materials involved. For intact units without leakage, smoke or fire involvement, use protective clothing appropriate to the task and electrical hazards. For damaged, leaking, smoking or fire-involved units, consult the SDS, current ERG and department SOP/SOG to determine respiratory and chemical-protective requirements.

Isolation & Evacuation

Use the current ERG Guide 171 for initial isolation and protective-action information when responding to a transportation incident. Distances and protective actions must be confirmed from the current ERG and adapted to the actual incident conditions.

Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 171).

First Actions for a UN 3499 Incident

Keep unauthorized personnel away from the incident area.
Stay upwind and uphill when practical and maintain a safe distance from damaged or overheated units.
Identify the shipment from the shipping papers, package markings and product documentation.
Do not handle damaged, leaking, smoking or overheated capacitors unnecessarily.
If a unit is involved in fire, follow the current ERG Guide 171 and incident-specific fire department SOP/SOG.
If electrolyte or other internal material has been released, prevent unnecessary contact and follow the product SDS for exposure and cleanup information.
Treat damaged capacitors as potentially energized until electrical isolation and safe handling have been confirmed.
Request HazMat or technical assistance when the product condition, electrolyte composition or electrical hazard is uncertain.

📋 Copy & Share Field Card

UN 3499 — Capacitor, electric double layer (with a

HAZMAT RADIO NOTE — UN 3499 Product: Capacitor, electric double layer (with an energy storage capacity greater than 0.3 Wh) Class 9 / Miscellaneous / ERG 171 PPE: PPE should be selected according to the incident conditions, product SDS and department SOP/SOG. Intact units that present no fire, leakage or exposure hazard may require routine protective clothing appropriate to the task. Damaged, leaking, smoking or fire-involved units may require additional respiratory and chemical-protective measures based on the known or suspected electrolyte and fire conditions. ISOLATION: Use the current ERG Guide 171 for initial isolation and protective-action information when responding to a transportation incident. Distances and protective actions must be confirmed from the current ERG and adapted to the actual incident conditions. ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO

Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.

=== IC HAZMAT BRIEFING === UN 3499 — Capacitor, electric double layer (with an energy storage capacity greater than 0.3 Wh) Class: 9 | Placard: Miscellaneous | ERG Guide: 171 Appearance: An electric double-layer capacitor is an energy-storage device that uses electrochemical charge separation rather than the conventional dielectric structure of a traditional capacitor. Commercial units commonly contain electrodes, a separator, an electrolyte and an external casing with electrical terminals. Water Reactivity: The intact assembled capacitor should not be assumed to be water-reactive. If the casing is damaged and electrolyte or internal materials are released, consult the manufacturer's SDS before selecting a cleanup or decontamination method. Extinguishing: For an external fire involving a UN 3499 capacitor, use the extinguishing agent and tactics appropriate for the surrounding materials and the current ERG/SDS guidance. Avoid actions that unnecessarily damage or rupture the capacitor casing. PPE: PPE should be selected according to the incident conditions, product SDS and department SOP/SOG. Intact units that present no fire, leakage or exposure hazard may require routine protective clothing appropriate to the task. Damaged, leaking, smoking or fire-involved units may require additional respiratory and chemical-protective measures based on the known or suspected electrolyte and fire conditions. Isolation: Use the current ERG Guide 171 for initial isolation and protective-action information when responding to a transportation incident. Distances and protective actions must be confirmed from the current ERG and adapted to the actual incident conditions. — Key Hazards — • The capacitor stores electrical energy and may remain electrically charged during transport or after equipment shutdown. • Damaged units may present electrical short-circuit, overheating, rupture or fire hazards. • A damaged casing may release electrolyte or other internal materials. — First Actions — • Keep unauthorized personnel away from the incident area. • Stay upwind and uphill when practical and maintain a safe distance from damaged or overheated units. • Identify the shipment from the shipping papers, package markings and product documentation. • Do not handle damaged, leaking, smoking or overheated capacitors unnecessarily. SOURCE: allfirefighter.com/hazmat/un/capacitor-electric-double-layer-un-3499 | Always use current ERG + SOP/SOGIC BRIEFING

Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.

UN3499 Capacitor, electric double layer (with an energy storage capacity greater than 0.3 Wh) Cls9 ERG171 | allfirefighter.com/hazmat/un/capacitor-electric-double-layer-un-3499SMS / 160 CHAR

Use for: Quick text to command or incoming units. Fits in a single SMS.

⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions. Page: https://allfirefighter.com/hazmat/un/capacitor-electric-double-layer-un-3499

Related UN Numbers in Class 9

Open Class Guide →Hazmat Hub →

UN 1350 UN 1365 UN 1841 UN 1845 UN 1931 UN 1941 UN 1990 UN 2071 UN 2211 UN 2212 UN 2216 UN 2315

Discovery block for training / quick reference. Always consult the current ERG + your SOP/SOG for operations.

Frequently Asked Questions about UN 3499

UN 3499 is the transport designation for a capacitor, electric double layer, with an energy storage capacity greater than 0.3 Wh. It is classified as a Class 9 miscellaneous hazardous material.

UN 3499 is assigned to ERG Guide 171. Responders should use the current edition of the ERG together with shipping papers, the manufacturer's SDS and local SOP/SOG.

An electric double-layer capacitor, or EDLC, is an energy-storage device that stores electrical energy through electrochemical charge separation. It is also commonly called a supercapacitor or ultracapacitor.

Yes. UN 3499 is assigned to Class 9, miscellaneous hazardous materials and articles.

Yes. A capacitor can retain stored electrical energy after it has been disconnected from equipment. Responders should treat an unfamiliar or damaged unit as potentially energized until safe electrical isolation has been established.

A capacitor can burn or contribute to a fire when damaged, short-circuited or exposed to sufficient heat. The exact fire behavior depends on the construction and internal materials of the specific product.

Damage can result in electrical short circuiting, overheating, casing rupture, smoke or electrolyte release. Avoid unnecessary handling and consult the product SDS and current ERG guidance.

Special Provision 361 addresses the energy-storage threshold and scope of the UN 3499 entry. Capacitors with an energy storage capacity of 0.3 Wh or less are not subject to the applicable requirements, and the entry does not apply to capacitors that by design maintain a terminal voltage, such as asymmetrical capacitors.

Sources (high level): DOT/PHMSA marking & class concepts + ERG usage principles. This page does not reproduce ERG guide text—always consult the current ERG for incident-specific protective actions.