A single-suction-point system in a basement or on a slab is typically a one-day job. Crawl space membranes and multi-point systems can take longer. The post-mitigation test starts at least 24 hours after the fan is switched on and runs at least 48 hours.
More detail
A typical Greater Cincinnati install day for a one-suction-point basement system runs roughly like this, though every house moves the clock a little. Around 8 a.m., the mitigator walks the basement with you, confirms where the pipe will run, and looks at natural-draft appliances such as a gas water heater venting into a chimney. From about 8:30 to 10, the floor is cored in the utility area and soil is dug out beneath it to form a suction pit; where the material under the slab is unknown, Ohio's standards require a communication test to confirm how far suction reaches. From about 10 to noon, pipe goes up through a closet or chase toward the attic, or out through the rim joist to the exterior. Early afternoon goes to mounting the fan in the attic, in a garage that is not under living space, or outside, since Ohio bars radon fans from basements and conditioned space, and to the electrical connection. Mid-afternoon covers sealing: urethane caulk along the floor-to-wall joint and around the suction point and plumbing penetrations, plus an airtight cover on any sump pit. The last stretch installs the manometer and marks its startup reading, applies RADON REDUCTION SYSTEM labels to the pipe and breaker, and runs a backdraft check on any natural-draft appliances. Crawl space membranes, second suction points, and pipe hidden through finished rooms can push the work into a second day. After that the calendar is set by rule rather than labor: Ohio requires you to be told in writing that the post-mitigation test should begin no sooner than 24 hours and no later than 30 days after the fan starts, and EPA recommends a two- to seven-day test. The radon mitigation systems page covers the full scope, and our closing timeline answer explains how the steps fit a home sale.