my tomato sauce that I keep in the fridge has been getting pressurized and will pop when I open it. It is so forceful that it splurts a little. The air inside is white but dissipates quickly after I open the jar. It just happened a second time. Is it still safe to eat? What is going on? More info: I'm not sure what the fridge temperature is but I have bought the exact same brand and had it be fine the entire lifespan of the product. It is entirely possible I accidentally used a spoon to pull out some sauce that was used for something else. 
This should not happen, and sounds like you have some fermentation happening in the jar.  I would suggest discarding.  In the future, use only clean utensils to reach into the freshly opened jar.  Refrigerate immediately after use, and use within about a week. 