Answer: Only members of the onion/garlic family will give off a strong odor of onions so I don't know which of your plants might be the cause. You might also look for rotting stems or overly soggy soils which can give off a sour smell. You may simply have to figure it out by moving one plant at a time to another room to see if that is the offending plant. It's difficult when you have a collection of plants to single out the problem without isolating individual plants. Just start at one end of the room and take a single plant out and put it in a smaller room (bathroom, perhaps?). If that's the one that's causing the odor, you'll know within 24 hours. If not, replace the plant and pull the next one. Eventually you'll figure it out!
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