To determine under what conditions a flammable refrigerant in the air will burn or explode, we need to understand the concepts of the Lower Flammability Limit (LFL) and the Upper Flammability Limit (UFL):
1. Lower Flammability Limit (LFL): This is the minimum concentration of the refrigerant in air at which it can combust. Below this limit, the mixture is too lean to burn.
2. Upper Flammability Limit (UFL): This is the maximum concentration of the refrigerant in air at which it can combust. Above this limit, the mixture is too rich to burn.
For the refrigerant to burn or explode, its concentration must be:
- Above the Lower Flammability Limit (LFL): If the concentration is below the LFL, there isn't enough refrigerant to sustain combustion.
- Below the Upper Flammability Limit (UFL): If the concentration is above the UFL, there is too much refrigerant, which dilutes the oxygen to the point that it won't support combustion.
Thus, the concentration must be within a specific range for combustion to occur.
In other words, the correct answer must satisfy both conditions: the concentration must be above the LFL and below the UFL.
So the correct choice is:
OD) At any concentration above the Lower Flammability Limit and below the Upper Flammability Limit.
