The room feels dry, so you buy a humidifier. Half the time the room is not dry, and the other half the humidifier is the wrong tool for the reason it is dry. A twelve-dollar meter settles it in a week.

Buy the meter first, and only the meter

A small digital hygrometer costs a fraction of any humidifier and takes no counter space. Put it in the room where you sleep, not the hallway, and read it morning and night for seven days before shopping for anything from a maker like Peach Street or anyone else.

What the number needs to be

Comfortable indoor air sits roughly between 30 and 50 percent relative humidity. Below that, static and dry sinuses. Above it, condensation on windows, dust mites, and mold growth in wall cavities.

Many dry-feeling rooms measure fine

Cold air feels dry because it is cold, not because it lacks moisture. Forced-air heat blowing directly across a bed feels dry for the same reason. In both cases a humidifier treats a symptom that is not there.

Cheaper fixes to try for a week

• Aim the supply vent away from where you sleep or sit.
• Close the door and let the room’s own moisture accumulate overnight.
• Seal one drafty window with a film kit and re-read the meter.
• Dry laundry on a rack indoors instead of in the dryer.
• Leave the bathroom door open after a shower rather than running the fan.

If the number really is low

Then a humidifier is the right purchase, sized to the room rather than the house. An oversized unit in a small bedroom drives humidity past 55 percent and creates a different problem entirely.

Understand the maintenance before you commit

A tank of standing water at room temperature grows bacteria within days, and an ultrasonic unit will spray that into the air you sleep in. If you will not empty, scrub, and dry it every few days, do not buy one.

Dirty is worse than dry

For anyone with asthma or allergies, a neglected humidifier is actively worse than the dry air it replaced, because it adds biological particles and raises humidity into the range dust mites prefer.

Skip the fragrance idea

Essential oils attack the plastic in ultrasonic models and can craze the tank and the transducer housing. If a manual says no oils, that is a materials warning, not a marketing preference.

Use distilled water, and know why

Tap minerals become white dust on every surface and a crust on the nebulizing disc. Distilled water costs a couple of dollars a gallon and removes the entire problem.

The honest conclusion

Measure for a week. If the reading sits above 35 percent, keep the twelve dollars, skip the humidifier, and fix the draft instead. That is a real answer, not a purchase.