One of the main reasons Federal Reserve policy makers have been able to keep monetary policy so stimulative in the face of an economic recovery is their steadfast confidence that inflation is, and will remain, quiescent.

But two new papers from the central bank challenge that outlook. One, published by the Federal Reserve Bank of St. Louis, warns price pressures may rise more quickly than thought in coming years. Another, from the Federal Reserve Bank of Richmond, notes the uncertainty of the Fed’s framework for divining the nation’s inflationary potential.

What happens with inflation is always a key matter for the Fed. But in the current environment, tame price pressures and the expectation they’ll stay that way are even more important.

Low inflation gives the Fed considerable breathing room to keep interest rates low and provide other forms of support in an environment in which economic growth is tepid and halting. If price pressures were to accelerate, the central bank would likely have to respond with a tightening in policy, even if economy was ill-prepared to deal with that action–a choice it would rather not have to make.

The St. Louis Fed paper, written by bank economist Kevin Kliesen, sees inflation risks coming from several sources. One problem spot could be that the Fed misjudges the economy’s ability to create price pressures. It’s possible policy makers will misgauge the so-called output gap, which is the difference between the economy’s potential–its ability to growth without fueling inflation–and actual rates of growth. The wider the gap, the lower the economy’s likely level of inflation.

“The size of the output gap might be smaller than conventional wisdom might believe,” Kliesen wrote. “If so, those who foresee little risk to the near-term inflation outlook because of a large, persistent output gap may be too optimistic.”

He also warns the Fed’s current policy stance–interest rates are effectively set at zero percent, mortgage asset purchases continue until the end of the first quarter–may distort financial markets.

“Although low interest rates are a key part of the FOMC’s strategy to boost economic growth and cement the health of the economic recovery, there might still be a danger of inflating asset prices by encouraging investors and speculators to shift out of low-yield assets like Treasury securities into higher-yielding assets like commodity contracts or other tangible financial assets,” Kliesen noted.

And while it’s not part of the Fed’s portfolio, huge government budget deficits also pose a risk to a stable inflation environment, he wrote.

The St. Louis Fed economist’s anxiety over the output-gap issue is backed up by Thomas Lubik, an economist at the Richmond Fed. In his paper, Lubik warns “uncertainty” over the correct way to measure the gap makes this concept, as central bankers now understand it, “a potentially faulty gauge” for assessing the economic situation and guiding monetary policy. That increases the chance of policy leading to a bad outcome.

Some of the worries shown by the Fed economists extend to the policy-making level. In a speech Thursday, Kansas City Fed chief Thomas Hoenig reclaimed his role as the most aggressive advocate for undoing the current state of policy. He said he’d like to see policy tightened “sooner rather than later” lest the central bank let inflation bloom and allow overly-easy policy to distort financial markets.

For now, however, most of the central bank’s weight rests behind maintaining the status quo of low interest rates. While the economy appears to be recovering, there is even a reappraisal of Fed’s mortgage-buying program now. The program is scheduled to conclude at the end of the first quarter but some officials are now leaning toward keeping the effort alive longer, fearing the critical mortgage market may not yet be able to function properly without Fed support.