Ventless Heaters & Carbon Monoxide Shutdowns: What You Need to Know

Most new ventless heaters have a safety feature called an Oxygen Depletion Sensor (ODS). This sensor turns off the heater if it detects low levels of oxygen or high levels of carbon monoxide.

Ventless Heaters and Carbon Monoxide Shutdowns

Understanding Ventless Heaters

Ventless heaters, also known as vent-free or unvented heaters, are a type of space heating appliance that does not need a chimney or vent to expel combustion byproducts. Instead, they release these byproducts directly into the room they’re heating. While convenient, this design raises concerns about indoor air quality and potential carbon monoxide poisoning risks.

The Carbon Monoxide Hazard

Carbon monoxide (CO) is a gas that is produced when fuels like natural gas, propane, wood, and coal are not completely burned. It cannot be seen or smelled. Breathing in a lot of CO can lead to poisoning, causing symptoms like the flu, dizziness, headaches, nausea, and, in severe cases, death.

Each year, the Centers for Disease Control and Prevention (CDC) report that over 400 Americans die from unintentional carbon monoxide (CO) poisoning. In addition, more than 20,000 people visit the emergency room due to CO poisoning unrelated to fires.

CO Exposure LevelsHealth Effects
35 ppmHeadache and dizziness within 6-8 hours of constant exposure
800 ppmDizziness, nausea, and convulsions within 45 minutes; unconscious within 2 hours
1,600 ppmHeadache, dizziness, and nausea within 20 minutes; death within 1 hour
Source: CDC

Oxygen Depletion Sensors (ODS)

Modern ventless heaters often have an Oxygen Depletion Sensor (ODS) or an Oxygen Depletion System (ODS) to reduce these risks. This safety feature monitors oxygen levels and turns off the heater when levels drop below 18-19%.

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According to the U.S. Consumer Product Safety Commission, “An ODS detects a reduced level of oxygen in the area where the heater is operating and automatically shuts off the gas to the burner before a hazardous level of carbon monoxide accumulates.”

How ODS Systems Work

ODS systems work by using a chemical sensor or an electrochemical cell to measure oxygen levels. When the oxygen levels get too low, the ODS shuts off the gas supply to the heater to prevent carbon monoxide buildup.

Manufacturers like Rinnai and Empire Heating Systems have integrated ODS technology into their ventless heater models, providing an additional layer of protection.

Importance of Proper Installation and Maintenance

While ODS systems offer a valuable safety measure, it’s crucial to follow the manufacturer’s instructions for proper installation and maintenance. This includes:

  • Ensuring adequate ventilation and airflow in the room where the heater is installed
  • Regular cleaning and maintenance to prevent sensor malfunction
  • Adhering to the recommended BTU input rating and room size specifications
  • Never using ventless heaters in bedrooms, bathrooms, or other confined spaces

Neglecting these guidelines can compromise the effectiveness of the ODS system, potentially leading to dangerous carbon monoxide accumulation.

Additional Safety Measures

In addition to ODS systems, it’s recommended to install carbon monoxide detectors in any room with a ventless heater and follow general CO safety practices, such as:

  • Never leaving a ventless heater unattended for extended periods
  • Opening windows periodically for fresh air circulation
  • Seeking medical attention if experiencing symptoms of CO poisoning

By combining ODS technology with proper installation, maintenance, and additional safety measures, ventless heaters can provide efficient and safer heating solutions when used correctly.

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I am a mechanical engineer and love doing research on different home and outdoor heating options. When I am not working, I love spending time with my family and friends. I also enjoy blogging about my findings and helping others to find the best heating options for their needs.