What is an ethical issue related to carrying out this investigation? Help Please?!?

After one inflation and deflation of a latex balloon, the rubber is stretched a bit and it will take a greater volume of air to get the same diameter. So you must use the same brand and color of the balloon to measure both people. One balloon per person. Besides, it's cleaner that way, for who wants to put their mouth on a balloon that has been blown up by someone else? The umption here is that both people you want to test are the same height, weight, and age. If there is a significant difference in any of the three, then the test results cannot be accepted. So here was three issues for ethics: identical balloons to prevent inaccurate test results, identical test subjects, and cleanliness.