Symptoms include pleuritic chest pain, substernal heaviness, coughing, and dyspnea secondary to tracheobronchitis and absorptive atelectasis, which can lead to pulmonary edema. Pulmonary symptoms typically abate 4 hours after cessation of exposure in the majority of patients.

Receiving an excessive amount of supplemental oxygen, a condition known as oxygen toxicity or hyperoxia, can lead to serious respiratory and neurological issues. The first signs often include a persistent, dry cough and a burning sensation in the chest or throat, especially when taking deep breaths. As the condition progresses, you may experience dyspnea (shortness of breath) despite being on oxygen, as the high concentration of O2​ can cause inflammation in the lung's air sacs (alveoli) or even cause them to collapse. Neurological symptoms are also common and include dizziness, a feeling of unease or "euphoria," confusion, and blurred or "tunnel" vision. In severe cases, particularly if the oxygen pressure is high, patients may experience muscle twitching in the face or hands, which can lead to full-body seizures. For chronic users of oxygen concentrators, another risk is "CO2 retention," where the body stops breathing deeply enough to expel carbon dioxide because it feels it has plenty of oxygen, leading to extreme lethargy and headaches. Always stick to the liter-per-minute (LPM) flow rate prescribed by your doctor.