Air Movers & Dehumidifiers

Notes

• These figures come from IICRC S500, the standard restoration contractors work to and insurers settle against. If you are checking an estimate, this is the same arithmetic the adjuster will use: 10 air movers and 80 AHAM pints per day for 400 ft² at Class 2.
• Air movers do not dry anything. They lift moisture out of materials and into the air. The dehumidifier is what removes it from the room. Running fans without enough dehumidification pushes that moisture into dry walls, into the ceiling cavity and into the next room — the most expensive mistake in the trade, and it does not show up for a week.
• Class is not the same as category, and people mix them constantly. Class is how much water — it sets the equipment above. Category is how dirty — clean supply water is Category 1, appliance or washing-machine overflow is Category 2, sewage or floodwater is Category 3. Category decides what has to be thrown away; class decides what has to be plugged in.
• Placement matters as much as count. Air movers go at a shallow angle to the wall, roughly 5 to 45 degrees, spaced to create one circulating path around the room rather than blowing at each other. Every corner and every offset needs its own unit because the airflow will not turn on its own.
• Measure, do not guess when it is dry. A moisture meter reading on affected material compared against a dry reference elsewhere in the house is the only way to know. Materials that feel dry to the hand routinely hold enough moisture to grow mould behind the paint.
• Power is a real constraint on a job this size. 10 air movers at roughly 2–5 amps each plus dehumidifiers at 5–9 amps will trip household circuits if they are all on one. Spread them across circuits deliberately, and expect the electricity bill for the drying period to be noticeable.