Funny you should bring this up -- I just got my NYC Health Dept. Food Protection certification week before last, so my manual and notes are handy!
For those not familiar with it, HACCP is a system originally developed by Pillsbury for the U.S. space program, to ensure a supply of safe food for astronauts. It is an acronym:
Hazard: any condition in which food can be contaminated
Analysis: likely problems are identified and their prevention determined
Critical
Control
Point: this is a step in which action must be taken to eliminate a hazard. Failure to do so will render the food unfit for consumption.
To quote the training manual we used:
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The HACCP system as decribed by the International Association of Milk, Food, and Environmental Sanitarians has a series of six inter-related steps:
Identify hazards and assess their severity and risks. The first step in this system is to review recipes to identify potentially hazardous foods or food containing potentially hazardous ingredients, set out the preparation process in a flow chart and identify the hazards that can occur at each step in the process.
Determine Critical Control Points. The second step is to identify the critical control points, that is, those steps where action
MUST be taken to prevent, reduce, or eliminate a hazard.
Institute control measures and establish criteria to ensure control. The third step is to determine the measures or the actions that are needed to prevent, reduce or eliminate hazards that are anticipated.
Monitor critical control points and record data. The fourth step is to monitor what is being done at each critical control point to determine whether the hazards are controlled by the actions set up in the third step.
Take action whenever monitoring results indicate criteria are not met. The fifth step is to put in place immediate corrective action if the hazards are not controlled at the critical control points.
Verify that the system is working as planned. The sixth and last step is to review the system to ensure that it is working, that hazards are identified, corrective actions are taken and that a safe food product is produced.
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Note: the manual for ServSafe inserts another step between taking action (#5 above) and verification (#6): Setting up a record-keeping system, to keep information (temperature of food, etc.) of importance in the process.
The "Food-Flow Diagram" breaks down every step from receiving to storage to preparation to cooking to hot holding (same day service), and cooling, storage, and reheating of leftovers, if done. The possible hazards at each of those steps are identified. If it is a step at which action must be taken to eliminate the hazard, it is flagged as a critical control point. Then the criteria for control at that step are determined, along with the monitoring procedure and the corrective action to be taken if the criteria are not met.
It is possible to write production recipes with the specific criteria built in. That way there is no question about how to avoid or correct problems.
As for using it at work ... you'll have to ask someone with a regular job!