Replacement columns are essential for keeping your Inogen One G4 portable oxygen concentrator in top shape. These replacement columns contain sieve beds that filter out nitrogen from the air to deliver high-purity oxygen, making them a crucial part of your device’s performance. Over time, these sieve beds wear out, which is why regular replacement is key to maintaining consistent oxygen delivery. When your G4 displays the “replace columns” alert, it’s time to switch them out. Fortunately, replacing them is straightforward and doesn’t require any tools—just follow the step-by-step instructions.