Flammability Characteristics and Metrics Flashcards
6 cards from real A2L practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Flammability Characteristics and Metrics flashcards as text
What does the Lower Flammability Limit (LFL) of a refrigerant represent?
Answer: The minimum concentration in air required to support combustion.
The LFL is a critical safety metric indicating the minimum concentration of a refrigerant vapor in air, by volume, that is capable of propagating a flame. Below this concentration, the mixture is too lean to burn. A higher LFL value means the refrigerant is less flammable.
How does the Minimum Ignition Energy (MIE) of an A2L refrigerant compare to that of an A3 refrigerant like propane (R-290)?
Answer: The MIE of an A2L is significantly higher than an A3.
A2L refrigerants are defined by their higher MIE (typically >10 mJ), making them significantly harder to ignite than A3 refrigerants like propane, which have a very low MIE (<1 mJ). This means a much stronger energy source, like an open flame, is required to ignite A2Ls, whereas A3s can be ignited by a simple static spark.
The '2L' in the ASHRAE 34 safety classification A2L signifies what?
Answer: Lower toxicity and a burning velocity of 10 cm/s or less.
The 'A' refers to lower toxicity. The '2L' denotes lower flammability, which is specifically characterized by having a maximum burning velocity of 10 cm/s or less. This slow flame propagation speed is a key safety feature of A2L refrigerants.
What is the Heat of Combustion (HOC)?
Answer: The amount of heat energy released when a refrigerant burns.
Heat of Combustion (HOC) is the measure of the total amount of thermal energy released when a specific quantity of a substance undergoes complete combustion with oxygen. For refrigerants, a lower HOC is desirable as it means less energy is released in the event of a fire, contributing to overall safety.
An A2L refrigerant is considered flammable only when its concentration in air is...
Answer: Between the LFL and the UFL.
For a flammable event to occur, the refrigerant concentration must be within its flammable range. This range is defined by the Lower Flammability Limit (LFL) and the Upper Flammability Limit (UFL). Below the LFL the mixture is too lean, and above the UFL it is too rich to burn.
Compared to A1 refrigerants, A2L refrigerants have:
Answer: Similar toxicity but a higher degree of flammability.
By definition, A1 refrigerants show no flame propagation when tested. A2L refrigerants are classified as having lower flammability, meaning they can propagate a flame under certain conditions, unlike A1s. Both A1 and A2L refrigerants fall into the 'A' category for lower toxicity.