Can You Use a Generator Indoors?

The short answer is no—portable generators should never be used indoors. This includes homes, apartments, garages, basements, sheds, or any enclosed or semi-enclosed space.

Despite this, many accidents occur each year because people underestimate the risks or misunderstand how generators work. This guide explains why indoor generator use is dangerous, addresses common misconceptions, and outlines safe alternatives for backup power.

Why Using a Generator Indoors Is Dangerous

Portable generators produce electricity by burning fuel. This combustion process creates exhaust gases, including carbon monoxide (CO)—a colorless, odorless, and highly toxic gas.

When a generator runs indoors, carbon monoxide can quickly build up to lethal levels, even if windows or doors are open.

Key risks include:

  • Carbon monoxide poisoning
  • Fire hazards
  • Oxygen displacement
  • Heat buildup

These dangers can occur within minutes.

Understanding Carbon Monoxide Risk

Carbon monoxide is particularly dangerous because it is difficult to detect without proper equipment.

Important facts:

  • CO cannot be seen or smelled
  • Symptoms may begin with headache or dizziness
  • Exposure can lead to unconsciousness or death

Generators can produce much higher CO concentrations than vehicles or household appliances, making indoor use especially hazardous.

Common Myths About Indoor Generator Use

“I’ll Just Use It in the Garage”

Garages—even with doors open—are not safe.

Carbon monoxide can:

  • Accumulate rapidly
  • Travel into living spaces
  • Remain trapped after the generator is turned off

Attached garages pose an even greater risk due to shared air circulation.

“I’ll Open Windows for Ventilation”

Opening windows or doors does not provide sufficient ventilation.

CO disperses unpredictably and can:

  • Re-enter the space
  • Build up in adjacent rooms
  • Reach dangerous levels quickly

Ventilation does not eliminate the risk.

“It’s Only for a Short Time”

Short-term use is still dangerous.

Carbon monoxide poisoning can occur in minutes, not hours. Even brief indoor operation can be fatal under the right conditions.

Are Any Generators Safe to Use Indoors?

Battery-Based Power Stations

Battery-powered portable power stations—sometimes called portable solar generators—do not produce exhaust.

These devices are safe for indoor use because:

  • They do not burn fuel
  • They emit no carbon monoxide
  • They operate silently

However, they are limited in power output and runtime and are suitable only for low-wattage devices.

Combustion Generators: Always Outdoors

Any generator that burns:

  • Gasoline
  • Propane
  • Diesel
  • Natural gas

Must be operated outdoors, regardless of size or noise level.

Safe Placement for Outdoor Generator Use

When operating a generator outdoors, follow these guidelines:

  • Place at least 20 feet from doors, windows, and vents
  • Direct exhaust away from buildings
  • Operate on a flat, stable surface
  • Protect from rain using approved covers

These precautions reduce—but do not eliminate—carbon monoxide risk.

Carbon Monoxide Detectors: An Important Backup

CO detectors provide an additional layer of safety.

Recommendations:

  • Install detectors near sleeping areas
  • Use battery-powered or hardwired units
  • Test regularly

Detectors should not be considered a substitute for proper generator placement but rather a secondary safeguard.

Why Indoor Use Is Especially Dangerous in Apartments

Apartments increase risk due to:

  • Shared walls and ventilation systems
  • Limited outdoor space
  • Proximity to neighbors

Carbon monoxide can affect multiple units, making indoor generator use not only dangerous but also potentially life-threatening to others.

Safer Alternatives for Indoor Backup Power

If indoor backup power is required, consider:

  • Battery-powered power stations
  • Uninterruptible power supplies (UPS)
  • Emergency battery packs

These options are suitable for:

  • Charging phones and laptops
  • Powering routers and lights
  • Supporting small medical devices

They are not replacements for full-size generators but offer safe indoor functionality.

What to Do During a Power Outage

During an outage:

  • Never bring a generator indoors
  • Never operate near open windows or doors
  • Follow manufacturer safety instructions
  • Prioritize ventilation and distance

Preparation and understanding are critical to safe generator use.

What Makes This Rule Non-Negotiable

Every major safety authority agrees on this point: portable generators must never be used indoors.

The risk is not theoretical. It is well-documented, immediate, and preventable.

Final Thoughts

Using a generator indoors is one of the most dangerous mistakes people make during power outages. Carbon monoxide exposure can occur quickly and without warning, even in well-ventilated spaces.

Understanding the risks—and knowing which alternatives are safe—allows you to prepare for outages responsibly. When it comes to generator safety, the safest choice is always the simplest one: keep combustion generators outdoors and use indoor-safe power solutions only where appropriate.