As Janet Yellen testifies in front of Congress this week, it is safe to say that she is facing the period of greatest economic uncertainty since she took over the role of Fed Chair roughly a year and a half ago.

The Federal Reserve appears to be rethinking its pace of interest rate increases, which most analysts had assumed would sit at 1% by years end, after turmoil in energy and emerging markets has shaken the confidence of American investors in the health of the global economy.

Another reason folks are concerned about the American economy is that we’re currently in the 80th month of this economic expansion, the 3rd longest in history. Janet Yellen has herself said that “expansions don’t die of old age.” And even though neither the Fed, nor most economists, are predicting a recession in the near future, it’s a good bet that the experts at the central bank are taking a look at possible recession triggers. Here are five that we should watch out for.