With a sufficient tank capacity and acceptable effectiveness, the Optimus U-31002 can meet your basic humidification needs. It is a quiet operator and offers a few extra "nice to have" features such as a night light, an included cleaning brush that is stored in the base, and a permanent ceramic filter. As you will read below, we questioned the function of the permanent ceramic filter, but we still liked this unit for its compact design and long run-time. Over time (and multiple cleanings), we began to like the design a little less due to the difficulty in accessing all surfaces. Despite cleaning difficulties, the Optimus's combination of performance and features placed it in the top four out of our nine contenders.
Optimus U-31002 Review
Pros: Compact, continuously variable mist output control, auto shut-off, night light
Cons: Difficult to clean, limited directional control of mist, shortest cord length
Our Analysis and Test Results
The Optimus U-31002 cool mist ultrasonic humidifier is easy to put together and use right out of the box. Its futuristic compact design accommodates a surprisingly large tank capacity of 4.5 Liters, and its night light's gentle glow is soothing in the dark. While we really like this humidifier while running as it is one of the quietest ones in our testing bunch, we were left disappointed that its attractive design doesn't necessarily translate into ease of use in terms of refilling and cleaning.
Ease of Cleaning
We place a lot of weight on ease of cleaning because regular cleanings are essential to maintaining positive health benefits from humidifier use. Unfortunately, with a 4 of 10 in this metric, its design doesn't make anything easier in terms of cleaning and weekly maintenance tasks.To begin with, the tank's curved top makes it very tippy when re-filling and cleaning and requires at least one hand for balance during these tasks. Though a bottle brush fits into the small opening of the water tank, but it can't be moved around adequately to clean the inside surfaces. A cleaning brush is included to clean the internals of the base, but it stores in the tank water which seems unhygienic. The base's small spaces also present difficulties for cleaning.
After one week of daily use with filtered reverse osmosis water, we noticed some pinkish-red film accumulate on the surfaces close to the brush sitting in the tank water. Hello, bacteria and mold! The instructions for the Optimus call for weekly cleaning using a diluted bleach solution. Though we aren't keen on using harsh chemicals to clean a machine that produces inhaled mist, visible microbe accumulation isn't a good deal either. So, pick your poison here.
With a 6 of 10 for effectiveness, this humidifier may not be as powerful as the Boneco U7147 Digital or the Vornado Ultra3, but it is generally effective at humidifying a smaller space. The manufacturer does not provide a recommended area for room humidification. However, our tests found that it was able to raise and maintain humidity for our testing space of approximately 120 square feet. Our in-home testing also found that it met our needs for a slightly larger space of about 200 square feet.
The U-31002 earned top marks with a score of 9 of 10 for its extremely quiet operation, placing it in the same class as Editors' Choice winner, the Sunpentown SU-4010, and Best Value, the Safety 1st 360. In fact, apart from occasional bubbling sounds as the tank emptied, the Optimus was so quiet that we had to place our ear next to the unit to hear any noise at all. It certainly doesn't disturb sleep or fatigue ears.
Ease of Use
Apart from difficulty with cleaning, there were many things we liked about the design of the Optimus. Earning a 7 of 10 in this area, its compact footprint easily fits on a night stand, and the large tank capacity provides more than enough water to function throughout the night. And, its auto shut-off feature protects the unit from overheating should the tank run out of water.A great bonus is that the night light functions separately from the mist output. And, in addition to the night light, there is no "on" light. Thus, the night light can be turned off during operation for zero light output. For slumbering souls who like absolute darkness, this is a great advantage.
The continuously variable mist output knob provides sufficient control over how much mist is desired. However, ability to control mist direction is limited; like the Crane Drop, the Optimus has only one removable mist outlet.Two big dislikes about this unit are the following. First, at 55 inches, the cord length is the shortest of all of our tested humidifiers and may acquire some furniture rearranging for close proximity to an outlet. Second, the permanent ceramic bead filter doesn't seem to do anything to reduce white dust or eliminate microbes. It is basically a small plastic cage holding visible ceramic beads the size of blueberries. We were unable find any information in the instructions or on the website explaining how this filter works, nor could we locate outside evidence to prove its effectiveness.
This humidifier is a good option for you if you are looking for a quiet, compact unit with a night light. Due to the difficulty in accessing all spaces during cleaning, we second the instruction manual's recommendation to use distilled or filtered water for best results.
The U-31002 is priced in the mid-range when compared with our nine tested models. When its features and performance are taken into consideration, it provides slightly greater-than-average value.
The Optimus U-31002 is an extremely quiet solid performer with the addition of a pleasant night light and a handy auto-shut of feature, but we are left disappointed due to design flaws that present themselves during cleaning and refilling of the tank. For about $30 more, consider the Sunpentown SU-4010. If budget is tight, go for the Safety 1st 360 to save around $20.
— Juliet Spurrier, MD & BabyGearLab Team