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1. Have physician-diagnosed asthma at least 1 year prior to the screening visit
2. Have evidence of uncontrolled disease as defined by at least one of the following:

Use of an asthma medication during the prior 12 months, report of asthma symptoms over the prior 12 months (wheezing/whistling in the chest)(3)

OR

One or more asthma-related hospitalization, emergency room visit

OR

Unscheduled clinic or urgent care facility visit resulting in a burst of systemic steroids (3 days or more of prednisone or equivalent; 1 or more doses of dexamethasone) in the previous 12 months

Exclusion Criteria

1. Not residing at the household for at least 5 days a week or family planning to move from the current home within the next twelve months, or homes with active radon mitigation systems (if home uses a HEPA filter air purifier, family must agree to disable the purifier for 28 days prior to randomization).
2. Lung disease, other than asthma, that requires daily medication (inflammatory diseases, chronic lung diseases aside from asthma, congenital cardiopulmonary conditions requiring medication or surgical treatment),
3. Homes with active HEPA filters will be excluded (even though the role of HEPA filters on radon and radon particles s is expected to be minimum and other exposures can be adjust for in the analysis)
4. Cardiovascular disease that requires daily medication, excluding hypertension
5. Taking a beta-blocker
6. Currently receiving unstable level of Immunotherapy (allergy shots)
7. Coordinator/PI judgment
8. Inability to perform lung function testing
9. Intake of abuse drugs or alcohol, have psychiatric disorders or severe mental disability that interferes with answering questions or following instructions.