If less air is inhaled then the accuracy is generally not greatly affected, if more gas is inhaled then the accuracy will be more affected. The urea breath test requires a capsule of carbon-13 or carbon-14 labeled urea to be taken before blowing, and then blowing half an hour later; H. pylori is able to secrete the enzyme urease, which breaks down labeled urea into carbon dioxide and ammonia, and the labeled carbon dioxide can be detected as it is exhaled with the breath. Therefore, if air is inhaled and then exhaled during the blowing process, the accuracy of the test may be affected; if less air is inhaled then the accuracy is generally not greatly affected, but if more gas is inhaled then the accuracy will be greatly affected. Patients who need to perform a urea breath test to detect H. pylori infection should standardize the test procedure to help maintain the accuracy of the results.