The Unseen IAQ Mennace

We’ve talked about all manner of Air Quality issues: pollen, viruses, volatile organic compounds, and more. There is however, one less frequently talked about devil in the air: radon, methane, and other ground seepage. These are harmful, either explosive, cancer-causing, or otherwise dangerous materials that can seep from the soil below. You’ll never know they’re there until it’s too late. How Does It Happen? Time for some science. The ground beneath you is not pure, solid dirt and rock straight to the Earth’s core. It’s not all one particular elemental composition either. There’s pockets of different materials, gasses, radioactive elements, and so on. These materials either work their way to the surface or they emit something that does. Consider for example, a gas like methane. This exists underground, in porous areas of rock or in large, hollow caves. It’s under extreme pressure from the rest of the Earth pressing down on it. All it takes is a path to the surface for it to flow out. When we do mining for it, we drill down and use a pipe to provide that path to the surface. The Methane is a low-density gas, it wants to move higher up, in the same way helium can make balloons float. There is some amount of natural seepage. The gas makes it way up through the ground and rock, tiny pores and cracks that let it slowly escape. The ground beneath you is not […]

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Why is the AC Hissing?

Air conditioners produce liquid water by design and by the simple nature of physics. Sometimes this harmlessly leaks out around the air conditioner, such as with window units, and sometimes it leaks when a drain gets blocked. There is however, a second leak an air conditioner can develop: refrigerant leaks.   The Cooling Compound Air conditioners work by exploiting physics around state-changes. When liquid turns into a gas, it can absorb heat.The effectiveness of the state change varies from compound to compound. For air conditioning, we tend to use things like R134a (freon), R12 (phased out/illegal in much of the world now), and even propane. These are all chemicals which have particular properties ideal for cooling. For example, they won’t turn solid at 0 degrees C like water, so they won’t clog up the air conditioner’s tubing and fittings. These chemicals though have some downsides we can’t really escape. Propane is outright flammable and probably capable of turning your air conditioner into a flaming set piece in the next post-apocalypse movie. R12 destroys the ozone. And R134a is toxic. It causes a wide range of symptoms from headaches to hallucinations and death in the worst case exposures.   The Hissing Leak When the air conditioner is running or has recently been run, the refrigerant will be highly pressurized. In order for us to make it work, we compress it. We’re cramming a lot of material into a small space, which […]

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Preventing CO2 Poisoning with Pressure

We have rollout switches and temperature sensors to prevent fires from spreading beyond the furnace. What about exhaust gasses? Almost every heating fuel we use produces deadly gasses. CO2, NO2, and more. If these gasses escape your furnace, you’re either going to leave the building or be killed by the gasses. It’s essential that we keep these gasses away from you. Your furnace has some very interesting ways of doing this and detecting a deadly hardware failure.   The Draft Inducer Older furnaces rely on physics and chemistry to get the CO2 out. As your furnace runs, it creates hot gasses. The hotter a gas is, the higher it rises in the atmosphere. As long as the exhaust is hot, it should rise up into your chimney or exhaust flue and be vented safely outside away from people. This isn’t entirely ideal, the exhaust is limited by the temperature difference, slowing it down. It’s possible for wind and other atmospheric conditions to disrupt the exhaust flow. There’s no mechanism to detect and respond to a blocked exhaust path. Modern furnaces don’t let the hot gasses just meander out the chimney. We use Draft Inducers, essentially blowers built just for furnace exhaust. These little blowers kick on a minute before ignition to vent the combustion chamber and usually remains on until after the furnace has shutdown. On the surface, this just makes the furnace burn cleaner. If there’s less carbon dioxide […]

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Catastrophic Furnace Failure

Furnace manufacturers are fighting day and night to make home, office and industrial heating safer. In large part these efforts are incredibly successful. When you hear of a home burning down, it’s more likely that someone left their stove on than a furnace malfunctioned. This of course, begs a few questions: Do furnaces still explode? What does it take for a furnace to explode? What happens if it does explode? Failure Upon Failure Depending on the furnace design, an explosion is going to need at least half a dozen separate pieces of equipment to fail or a fair number of absurd design flaws in order for anything to happen. The pressure relief valves have to fail and become stuck shut. The furnace’s controller has to ignore or never see excessive temperature and pressure readings. The entire furnace has to run until it’s built up sufficient heat and pressure to actually explode, which it would likely never do under a regular duty cycle. A pressure explosion needs everything to go wrong. These are the sort of odds that make winning the lottery look easy. Even so, with seven billion people in the world and likely just as many heating systems having been built, failures happen. Just, what doe sit look like? Creating a Failure The only way to see a failure is to make it happen. Luckily, the Mythbusters have done this for us. It goes without saying, do not disable […]

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