What is a key characteristic of rescue inhalers in asthma treatment?

Rescue inhalers are specifically designed to provide immediate relief during an asthma attack by delivering a fast-acting bronchodilator medication directly to the lungs. This rapid action helps to quickly open the airways, alleviating symptoms such as wheezing, shortness of breath, and chest tightness.

In contrast, the other options do not accurately reflect the function or use of rescue inhalers. For example, they are not intended for daily maintenance—those typically involve long-term control medications that are used regularly to manage asthma over time. While they are critical in emergencies, they are not exclusively prescribed for such situations; many patients are instructed to carry them at all times in case symptoms arise. Additionally, while some inhalers can be used with spacers for better delivery of medication, rescue inhalers can be effective on their own without a spacer. Therefore, their primary purpose is to provide quick relief when an asthma attack occurs, making the identification of option B as the correct answer clear.