Boilers are still used to heat many of the homes in the United States today. They're reliable and efficient, and because they use natural gas or propane, they're money savers in areas where the price of electricity is high. Boilers, like furnaces, have a tendency to smell bad when something goes wrong. While you shouldn't rely on your nose alone, the type of odor you detect from the boiler can give you a hint as to what the problem is. Here are three smells you may notice and what they may indicate.

Egg Smell

If you detect an egg-like odor coming from your boiler, call a technician right away. The smell could be a result of poor burner or flue performance, but a gas leak is the likely culprit. Although natural gas is odorless, chemicals are added to it to give it a distinctive odor for detecting leaks. Most describe the smell as rotten eggs, bad cabbage or a hydrogen sulfide odor.

The rotten egg smell is also common in both boilers and water heaters when bacteria begins to grow. It's not dangerous in those cases, but it is unpleasant. It results from the growth of anaerobic bacteria in the magnesium and aluminum parts of the boiler. The anodes may need to be replaced to get rid of the bacteria and egg smell.

Gas Smell

The gas smell is different than the rotten egg smell because the gases are different. Many boilers are fueled by natural gas or liquid propane. As mentioned above, natural gas has an additive to make it smell like rotten eggs. Propane, however, just smells like a gas.

If you notice a gas-like smell, check to see if the gas valve has loosened. You can do this by spraying the fittings with a mixture of soap and water to see if bubbles appear. If they do, tighten the valve with a wrench. Should you still notice the gas smell after you've tightened the valve, contact a boiler technician. The problem may be the outflow getting sucked back into the inflow pipe outside your house.

Rotten Smell

If you notice a rotten smell when you operate the boiler, you could have a dead bird or rodent somewhere in your home. Strong smells may indicate an animal or bird in the flue. But a dead animal under the floor or walls near the boiler would also give off a strong smell as the boiler heats up.

No matter what the odor is, you should never go by your sense of smell alone when diagnosing boiler problems, especially if you suspect a gas leak. Some people have a diminished sense of smell, or the odor may be masked by something else in the environment. Other variables can also fade the odor, making it virtually undetectable to the nose.

In addition to odor, look for the following problems when inspecting your boiler and lines:

• Exposed pipelines in the yard
• Moist areas above the pipelines
• Damaged connections in or under the house
• Hissing or whistling sounds

If you have any doubts as to whether what you're smelling is a gas leak, open the doors and windows and get everyone out of the house. Call 911 or your nearest emergency services, and they'll dispatch someone to your home to investigate. If it will be a while before someone can come out to your house to take a look, stay with a friend or relative until you are sure that conditions inside are safe.

Don't try to tackle repairs on your own. Unlike furnaces, boilers contain a lot of pressure, and unskilled DIY repair attempts may result in an explosion. Call a boiler repair service like HomeSmart From Xcel Energy for professional assistance with any of the above problems.