Special handling instructions for breakage are not printed on the packaging of household CFL bulbs in many countries. The amount of mercury released by one bulb can temporarily exceed U.S. federal guidelines for chronic exposure. "Chronic", however, implies exposure for a significant time, and it remains unclear what the health risks are from short-term exposure to low levels of elemental mercury. Despite following EPA best-practice clean-up guidelines on broken CFLs, researchers were unable to remove mercury from carpet, and agitation of the carpet — such as by young children playing — created localized concentrations as high as 0.025 mg/m3 in air close to the carpet, even weeks after the initial breakage.