thermal sensor accuracy
If you are designing a product using this sensor then the best way to get rid of inaccuracy is calibration. 

You will need to use an accurate black body source to calibrate your product. You will need a range of black bodies to use as a reference and design in a calibration routine. It will need some work doing before all this, as you'll need to test the sensor in steps throughout the temperature range to plot a graph to figure out the temperature response. The less linear the response, the more calibration points you'll need. Infrared measurement is a pain to calibrate accurately so you'll need a temperature controlled environment to do it in too. 

This can end up getting expensive so it depends how critical accuracy is. But to summarise, the short answer is calibration.