Detecting unstable nitrate film is by far the most important way to preserve this material. If decomposition isn't found quickly, complete destruction of the film record may result. Spot inspection only needs to be done once a year if you follow the recommended storage conditions, and once every 3 months if adverse conditions exist. Any nitrate film that is badly buckled or sticky is in an advanced stage of decomposition. You may be able to duplicate some of these badly buckled or deteriorated films, or they may yield a fair quality print.
Urgency is the word.
If the film base is heavily stained and moisture from our breath makes the gelatin slightly sticky, the negatives or prints must be duplicated within 2 years while maintaining proper storage conditions. If you must remove surface dirt, use a quality cleaner carefully. Many old negatives have an iridescent dichroic or silver sulfide stain, usually on the surface of the gelatin. This is a further sign of old and deteriorated film. Store these negatives only in small quantities and in different locations.