Can a Propane Heater Explode?


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People use propane heaters for garages, sheds, and other outdoor uses. Others may want to use them inside an RV or even in their homes as a primary heating source. But is there a danger that a propane heater can explode while you’re asleep?

A propane heater can explode, given the right conditions. Propane gas is highly combustible, and when mixed with air, a spark or other ignition source can initiate a fire. The resulting heat can cause the pressurized propane cylinder to fail and trigger an explosion. 

In the next sections, I will explore why propane heaters can explode and how to prevent it from happening. I will also discuss other potential hazards and steps to avoid them. Finally, I will recommend some of the safest propane heaters currently available. 

Why Propane Heaters Explode

Some of the larger outdoor-use heaters have a 20lb propane tank attached by a hose. The smaller, portable heaters come with a one-pound mini cylinder already attached. 

Two conditions can cause either type of propane heater to explode:

Propane Leaks

Propane is heavier than air, so it can drop into tight spaces when it leaks out. The result can be catastrophic if it settles near a heat source such as a pilot light, open flame, or the unit’s heating element. 

Propane leaks typically occur in one of four areas: 

  • The connection hose. In larger units, the heater element is connected by a hose to a 20lb propane tank. The connections at the end are where the most leaks occur. The hose itself can also leak due to cracks and other damage. 
  • The pressure regulator. Large outdoor heaters connected to a 20lb tank require a pressure regulator between the tank and the heater. Most of the time, these regulators are built into the hose. Some are separate components of larger systems. Either way, these regulators can get worn out and leak, either on the outside or internally. In most smaller, portable units, the pressure regulator is built into the heater, so these types of leaks seldom exist. 
  • The propane tank shutoff valve. 20lb tanks and larger have shutoff valves. As with the pressure regulator, the shutoff valve is susceptible to leaks if worn or damaged. Portable units do not have shutoff valves since they screw directly into the heater. 
  • The propane tank. Although not likely, propane tanks can leak, especially if there is rust or damage present. 

Explosions Caused by the Overpressure of Propane Tanks

Propane’s boiling point is -44° F. That means, since it is stored as a liquid, it turns into a gas at temperatures above -44° F, leading to pressure buildup in the storage cylinder. For this reason, it is best to store propane in a cool, dry area. 

Excess pressure is usually not a problem since propane cylinders are built to withstand it. They also have a relief valve built into them to vent maximum pressure before it becomes a problem. 

However, sometimes the pressure relief valve can fail to do its job when the cylinder temperature rises too quickly, as in a flash fire. The pressure increases so fast that the relief valve doesn’t have time to open. The result is a rapid, excessive pressure buildup to the point where the cylinder fails and then explodes. 

In rare cases, the relief valve will fail. If the temperature exceeds the cylinder limits, it could also cause an explosion, even if the temperature rises slowly. What’s worse, it can cause a chain reaction with other stored cylinders. That’s what happened in this video:

Preventing Propane Heater Explosions

Here are a few steps to take, which will minimize the risk of explosions:

Step #1: Check for obvious damage. The propane tank should be free of rust and dents. Hoses should be pliable and free from cracks. Hose connectors, where most leaks occur, should not have any cracks or dents.  

The heater should also be free from damage. If it is over 10 years old, consider replacing it. 

Step #2: Check for leaks. The most obvious way to detect a propane leak is by smell. If there is a rotten-egg odor present, there may be a leak somewhere. 

Verify it by mixing a few drops of dish soap into a spray bottle full of water. Spray the soap solution around the hose, valves, and connections. Air bubbles will be present if there is a leak. 

Watch this video to get detailed instructions:

Step #3: Position the heater on the floor in a well-ventilated area. Never use large patio heaters inside. When using a portable model, it is vital to keep children away from the heater. Keep other objects away also while in operation.

Most newer heaters come with a safety device at the bottom that cuts power to it when it is knocked over. It is best to test this feature before every use. 

Other Hazards To Avoid

The most immediate danger for users of portable propane heaters in the home is carbon monoxide poisoning and oxygen displacement. Since propane is heavier than air, it replaces the oxygen in an enclosed room and lowers it down to dangerous levels. 

Some propane heaters come with a built-in gas meter that detects carbon monoxide and oxygen levels—an alarm sounds when there is either not enough oxygen or too much carbon monoxide in the air. 

Firefighters conducted a test of the most popular, portable model to see how long it would take for the alarm to sound. The results are here in this video:

Oxygen and Gas Detectors

One way to stay safe when using a portable propane heater indoors is to invest in an oxygen/gas detector. There are several models to choose from. Some are hard-wired into the home’s electrical circuit, while others are fully portable. 

One of the best portable detectors is the OXYGEN Detector by FORENSICS. It can detect both the lack of oxygen and the presence of harmful gasses in the home. 

What Are the Best Propane Heaters To Buy?

There are so many choices when buying a propane heater. Here I chose the best out of each category to recommend as a starting point. 

Probably one of the most elegant and functional heaters for the patio is the Hiland HLDSO1-WGTHG Pyramid Patio Heater with an electronic igniter and Quartz Glass Tube Flame Heater. It combines beauty, style, and convenience all in one heater.

For construction crews and mechanics who want to stay warm in the winter, the Sunnydaze 40,000 BTU Forced Air Propane Heater is an obvious choice. It comes with a regulator and 10 feet of hose to connect to a 20lb propane tank ( not included). 

The Mr. Heater MH18B Propane Heater is for campers, RVers, or anyone who wants to get warmed up fast. It puts out a lot of power for such a compact, convenient unit. 

It features a built-in low-oxygen shutoff system (ODS) that sounds an alarm if oxygen levels get too low. It also has an auto-shutoff function if the heater tips over, helping to prevent accidental fires. 

Final Thoughts

There are several hundred propane-related fatalities each year, according to the Occupational Safety and Health Administration (OSHA). Another 600 are injured from propane explosions, according to the Consumer Product Safety Commission. 

Avoiding injury can best be accomplished by reading the manufacturer’s safety guidelines, following them, and applying some common sense.

Steve Rajeckas

Steve Rajeckas is an HVAC hobbyist with an avid interest in learning innovative ways to keep rooms, buildings, and everything else at the optimal temperature. When he's not working on new posts for Temperature Master, he can be found reading books or exploring the outdoors.

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