Dangers of Using Unvented Gas Heaters

Ventless gas heaters sound like a good deal at first:

  • They’re inexpensive.
  • Can be located almost anywhere in a house.
  • Don’t require an expensive vent pipe or much in the way of installation cost.
  • They’re efficient.

These attributes can make them attractive solutions for many homeowners, but make no mistake, they are dangerous. Even with careful maintenance and followed recommendations for safe usage, Unvented gas heaters pose several threats. Here are the three real dangers of using unvented gas heaters.

Fire Risk

  • Improper installation, positioning, and maintenance are the most common reasons why these heaters create housefires. These heaters can still be a fire danger in smaller spaces if placed near combustibles such as furniture, fabrics, and paper.
  • Allowing them to run for too long or running them unsupervised, especially with pets or children, are also dangerous causes for house fires.

Unvented Gas Heaters May Cause Health Issues:

Natural gas and propane heaters significantly impact indoor air quality and, as a result, can become a severe health concern.

  • Ventilation is needed to remove pollutants such as carbon dioxide and carbon monoxide. Unvented gas heaters do not have this option, though, which makes them not only dangerous but also falsely boosts their heating efficiency.
  • According to the National Fuel Gas Code, one air change per hour (ACH) would mean that a room that measures 10×20 feet would see a 25% reduction in the efficiency of a 3,800 Btu/hr unit.
    • Since air changes are less likely to happen with an unvented heater, they are seen as more efficient than they should be and are more dangerous.

Carbon Monoxide

  • Carbon monoxide, at low levels, causes long-term health issues. At higher levels, it is toxic and potentially fatal. Carbon monoxide is a non-irritating, odorless, colorless, and unnoticeable gas. Only carbon monoxide deters can detect it.

Carbon Dioxide

  • Carbon dioxide, while not considered toxic, poses several health risks. Increased carbon dioxide exposure causes headaches, dizziness, restlessness, tiredness, elevated blood pressure, asphyxia, and in severe cases, convulsions and coma.

Nitrogen Dioxide

  • Nitrogen dioxide can affect immune systems while raising susceptibility to respiratory infections, even when people are only exposed at minimal levels.
  • Because some nitrogen oxide is always produced in a flame, it is credited with increasing asthma, cough, sore throat, even nausea, and vertigo. Long-term effects of exposure to this gas can be chronic lung disease such as emphysema.

Sulfur Dioxide

  • When gas doesn’t burn completely, some carbon molecules become soot, which is proof of carbon monoxide in the space.
  • If the unvented gas heater uses natural gas, then methyl mercaptan is added to the mixture. It causes that sulfuric rotten egg smell that allows you to notice the leak. When methyl mercaptan burns, it creates sulfur dioxide that can irritate the eyes and the respiratory tract.

Humidity Damage:

  • These appliances also create unwanted levels of humidity and condensation.  This condensation directly results from the heater’s efficiency and the creation of methane that is released into the room.
  • There is no vent to collect the water vapors produced in the creation of heat, the water vapor moves into the open space.
  • Adding too much humidity to an area can result in the following:
    • Wooden furniture may warp and rot.
    • Paint and wallpaper may begin to bubble and peel.
    • Mold may grow within the plaster.
    • Severe health problems for homeowners, especially those who have allergies or asthma.

How to Make Unvented Gas Heaters Safer

Most unvented gas heaters are small units intended for emergency use or in small areas, typically a single room. Some models offer options for minimal ducting or fans.

They can also be wall-mounted or used as fireplace inserts to give a traditional wood fire’s realistic appearance and feel; most range in heat output between 5,000Btu/hour to 30,000Btu/hour. This source of fuel-powered heat can be an excellent form of backup heat, making it a desirable option for some families.

If you decide to use an unvented fuel heater, please adhere to the following advice.

  • Get Professional Installation
    • All unvented gas heaters should be installed by a professional. They are aware of the risks, have taken training, and know-how to spot hazards that the average homeowner may overlook. Their expertise and judgment may protect you, your family, or your home.
  • Use Oxygen Sensors
    • It is recommended that only approved unvented gas heaters be used. Approved heaters will have Oxygen Depletion Sensor (ODS) pilots, which shut off gas flow when oxygen levels in the space drop to 18.5% or lower. For reference, normal air levels linger around 21%.
  • Use Appropriate Spaces
    • A professional installer would be able to determine the proper heating unit for your space; their knowledge is invaluable.
  • Install a Carbon Monoxide Detector
    • Homeowners would also be wise to install a digital display carbon monoxide detector that is listed as “sensitive.” Carbon monoxide is deadly because it is odorless, colorless, tasteless, and otherwise undetectable to humans.

While unvented gas heaters are compact and initially cost-effective.

  • Vented gas heaters are typically more economical, efficient and are safer in the long term.

If you decide to use an unvented gas heater in your home, hire a professional to install it. Be sure to maintain the heater properly, install detectors, and follow its general safety protocols. Create some sort of ventilation for the space, and never allow the heater to run more than four hours at a time.