Honeywell HCM-350 Series

If something's not right

• Fan runs but the water level in the tank doesn't drop

  Likely cause: The filter has dried out, the room is already above 60% humidity, or the upper enclosure/tank isn't seated

  Fix: Check or Adjust — Rinse a dry filter under cool water and refit it wet; check the room's humidity; reseat the upper enclosure and water tank.

  Source: manufacturer

• The filter has turned light brown or rust-colored

  Likely cause: Mineral deposits — not a worn-out filter

  Fix: Check or Adjust — Soak the filter in cool water to loosen deposits; the discoloration may stay but doesn't affect performance.

  Source: manufacturer

• The power light turns from green to red

  Likely cause: The UV bulb needs replacing (it averages about 3,000 hours)

  Fix: Professional Service — Contact Honeywell (Kaz) consumer relations for a replacement bulb, part HCM-350-UV.

  Source: manufacturer

• No visible mist

  Likely cause: Normal — it's an evaporative humidifier and releases invisible moisture

  Fix: Check or Adjust — Watch the tank level instead: if it drops over 24 hours, it's working.

  Source: manufacturer

Maintenance schedule

1. Rinse and refill with fresh water

   every day · Easy

   On days you use it, rinse the unit out and refill with clean water. Source: https://www.honeywellstore.com/store/news/honeywell-humidifier-cleaning-guide-2020.htm

2. Descale and disinfect

   every 7 days · Moderate

   Remove the filter first. Scale removal: wipe base, tank cap and tank with undiluted vinegar. Then, separately, disinfect with 1 tsp bleach in 1 gallon of cool water and rinse until the smell is gone — never mix vinegar and bleach. The tank and tray are top-rack dishwasher safe (no detergent); the tank cap, filter and housing are not. Sources: https://www.honeywellstore.com/store/news/honeywell-humidifier-cleaning-guide-2020.htm and https://www.honeywellstore.com/store/images/pdf/honeywell-hcm-350-humidifier-manual.pdf

3. Replace the wicking filter (Filter A)

   every 45 days · Easy

   Every 30–60 days depending on water quality and use. Soak the new filter in cool water before fitting; don't wring it. Sources: https://www.honeywellstore.com/store/products/honeywell-uv-cool-moisture-germ-free-humidifier-black-hcm-350b.htm and https://www.honeywellstore.com/store/images/pdf/honeywell-hcm-350-humidifier-manual.pdf

   Uses: Honeywell Replacement Wicking Filter A (3-Pack)

What keeps the HCM-350 Series running