Final answer:
The woman's burn, characterized by painful reddened skin without mention of blistering, is indicative of a partial thickness burn. Using the 'rule of nines', the arms and face coverage would total 22.5% BSA, but the most likely classification based on the given details is a partial thickness burn involving 18% BSA.
Step-by-step explanation:
When considering the case of the woman who experienced a sudden burst of flame while lighting a gas grill, we need to classify the type of burn she suffered. Burns are categorized by both their severity and the total body surface area (BSA) they affect, commonly measured using the 'rule of nines'. Given that she has painful reddened skin on the front of both arms and her face, but the description does not mention blistering or deeper tissue damage, the burn would be classified as a partial thickness burn, which affects both the epidermis and a portion of the dermis.
Using the 'rule of nines', the BSA for the arms and the face would be calculated as follows: each arm represents 9% of the BSA, totaling 18% for both arms. The face represents roughly 4.5% of BSA. Adding these amounts, we get a total of 22.5% BSA. However, since the provided options do not include this exact percentage, it is likely that not all of these areas are fully covered by the burn. Solely, arms could be the most affected with 18% BSA. Therefore, considering the description and provided options, the most accurate classification for the burn would be a partial thickness burn involving 18% BSA.