Embodiments of the disclosure can include biomarkers for systems, methods, and devices for detecting and identifying certain substances, such as chemicals, volatile organic compounds (VOCs), volatile gases (VGs), ketones, cannabis, controlled substances, pharmaceuticals, or anesthetics, in the exhaled breath of a subject or person in real-time; and further diagnosing, treating, and addressing one or more associated health conditions or diseases, including a virus, such as COVID-19, tuberculosis (TB), lung cancer, or chronic obstructive lung disease (COPD).