Let’s talk about fixing natural gas lines – especially the half-inch to one-and-one-half inch size plastic lines commonly used as service feeds to residential homes. Gas utility owners state very clearly that they only want their own personnel to repair damaged or leaking gas lines.
Natural gas comes from the earth and is a byproduct of the decomposition of plants trapped beneath its surface. This gas is mainly methane, the most simple hydrocarbon molecule. It has a heat value of about 1000 BTU per cubic foot of gas. By comparison, propane has a much higher heat value of about 2500 BTU per cubic foot of gas. While natural gas does burn, it isn’t the most efficient in terms of heat generated. This helps us understand the explosive characteristics of natural gas. It’s important to understand that it takes a lot of oxygen to sustain the burning or the explosion of natural gas.
Natural gas burns or explodes within a very narrow concentration range. According to gas utilities, the flammable range of natural gas is between four and 15 percent gas in air. This means if there is less than four percent gas in the air, it’s too lean to burn. If there is more than 15 percent gas in the air, it’s too concentrated to burn; the concentration is too rich (similar to flooding your car’s engine with too much gas). This narrow range might make you feel like natural gas isn’t dangerous. That is exactly why the gas companies don’t want anyone other than their employees to do anything around a leaking gas line. It’s more dangerous than you think, and it’s hard to know if the gas concentration is in a relatively safe zone. Gas company personnel use special gas monitors to determine the gas concentration in the air and then determine how and when to respond.
When the gas concentration is within the four and 15 percent range, it only takes a spark to ignite the gas. The most common spark source is static electricity. The simple friction of gas flowing through a line, or rubbing your hands against your jacket can build up a static charge that could spark an explosion.
Gas companies train personnel in grounding lines and tools to prevent static discharge. Utility personnel are also experienced at using gas concentration meters.
It’s important not to damage gas lines. Utilities designed the one-call system to help locate lines so you can avoid them while you’re working. Following the regulations about safe-dig zones and using hand tools, vacuums or hydro techniques to expose lines also helps prevent damage. However, even with care, we can sometimes damage a gas line. If this happens, don’t attempt to repair it yourself. Call the gas company, and let their crews handle it.