Radon is one of the many potential health hazards in your rental. Certain areas of the U.S. are more prone to radon than others. If you have reason to believe that you have a radon problem in your rental unit, you'll want to have your place tested, either with a do-it-yourself radon test kit or by hiring a professional radon contractor. Landlords might be liable for tenants' injuries caused by radon, so it's reasonable to ask your landlord to pay for the radon testing. You can use this sample letter as a model in preparing your own.
If your letter doesn't get results, you might consider buying an inexpensive radon test kit yourself and then using the results to motivate your landlord to take further action. You can use the sample letter below as a template for writing to your landlord.