This refers to the concentration of sodium hydroxide solution needed for sterilizing medical equipment

See:
http://forums.futura-sciences.com/chimie/208099-definition-s...
http://www.newton.dep.anl.gov/askasci/chem99/chem99456.htm

For examples of use in a related context, see:

"Immerse in 1N NaOH or sodium hypochlorite (20,000 ppm available chlorine) for 1 hour)"
http://www.cdc.gov/ncidod/dvrd/cjd/qa_cjd_infection_control....
That's from the Center for Disease Control on prion sterilization

"....cleaning of the device and sterilization using a combination of sodium hydroxide and autoclaving [36] (e.g., immerse in 1N NaOH for 1 h, remove and rinse in water, and then transfer to an open pan for autoclaving for 1 h [at 121°C in a gravity displacement sterilizer or at 134°C in a porous or prevacuum sterilizer])"
That's from an article published in the "Clinical Infectious Diseases" journal

"Contaminated items such as scalpels, needles, surgical instruments, etc., immersion in 1N sodium hydroxide for 1 hour at room temperature followed by steam sterilization at 121°C for 30 minutes has been found to be effective."
http://www.colorado.edu/ehs/pdf/Biosafety-EMS.Disinfectants ...
That's from the University of Colorado at Boulder's "Guidance Document for Disinfectants and Sterilization Methods"