We ask, is it possible to get a balance between speed and noise in a hand dryer that satisfies the user. Of course faster airflow and particularly fast, condensed airflow is going to create more noise, so it’s a real challenge to hand dryer designers and engineers to create a dryer that people are happy with the performance, the noise levels and the energy efficiency,
Blade hand dryers
The Mitsubishi Jet towel is an example of a product that nearly meets this objective. Our independent results* measured the Mitsubishi Jet Towel at 75 dB(A) in a anechoic chamber (sound proof room) with hands placed into the airflow for a realistic noise measurement. 75 dB(A) is considerably higher than the 58 to 64 dB(A) advertised for the Mitsubishi Jet Towel however the generation 8 model dries relatively quickly (around 16 seconds in stringent test conditions, less in normal circumstances) and it uses as little as 0.55kw rated power. 75 dB(A) on a scale using deafening, very loud, loud, moderate, faint and very faint to describe would be on the lower end of loud, very few people would be expected to be irritated by this level.
It must be noted though that this measurement did not take into account noise amplification in a normal room, a previous study at Intertek revealed the Mitsubishi Jet Towel hand dryer measured at 79 dB(A) in a representative room. Upper 70’s in dB(A) are considered to irritate a small minority of people but with a hand dryer it is a very short lived experience, certainly in terms of safety, 80 dB(A) is considered safe for up to 8 hours exposure per day so there is no issue from this perspective. A little more detail about pitch is needed to complete the overview of the perceived sound on hand dryers but from this basic information the Mitsubishi Jet Towel achieves a good balance.
From a hygiene perspective, it has NSF approvals, although these kinds of approvals are done based on testing on brand new hand dryers. What is important is how hygienic the hand dryer will be 2 years after installing. The nature of this hand dryer with its water collection means that it must have a thorough and regular cleaning routine to maintain optimum hygiene standards.
The information we have on the new ‘quieter’ Dyson Airblade DB is incomplete, we only have a measurement in the sound proof chamber at 80 dB(A). You would expect a 4-5 dB(A) amplification in a normal room, if it followed the same pattern as the Mitsubishi Jet Towel and other dryers. Again, there is no safety issue at these levels considering the short term exposure but some users will certainly find these noise levels irritating. The Dyson Airblade DB is certainly fast drying (13-14 seconds in our stringent test and less than this under normal conditions) and uses an acceptable if not low rate power of 1.6kw. We have to say, based on the evidence, if you are looking for a good balance between energy efficiency, speed and noise the Mitsubishi is the overall winner here. With regards to hygiene, the same applies as with the Mitsubishi Jet Towel, all testing is based on a brand new unit, although the Airblade does not collect water if the HEPA filter is not properly maintained and cleaned there will surely be a difference between the hygiene levels provided by a new unit and one two years into its life.
‘Hands under’ type hand dryers.
The Dryflow Classic PLUS and Dryflow Elite are two dryers that are designed specifically to meet the objective of achieving an acceptable performance, at a quiet sound level with reasonable levels of energy efficiency. Another positive is that they are both very affordable hand dryers with outstanding motor lifespans. The Dryflow Classic PLUS is not a super-fast dryer but it is solid, it combines 45 m/s air speeds (traditional dryers 20-30 m/s, high speed 70 m/s upwards) with heat to achieve an approximate 20 second dry. The independent test measured the dB(A) at 72 in a sound proof chamber with hands under and because the Dryflow Classic PLUS is not relying purely on rapid airspeed we would expect amplification in a normal room to be minimal. We would describe this hand dryer as an excellent compromise, reasonable fast if not spectacular, with a very tolerable noise level with a rated power of just 1.35kw giving an energy efficient, if not hyper low energy performance. The Dryflow Classic PLUS is vandal resistant, very long lasting and at a price point where it is affordable for all. I guess the only question mark is that mild heat, in theory will increase bacteria levels if the dryer is not internally sanitized, we don’t have any clear evidence of this put this is the argument that has been pu forward by the paper towel companies for many years.
The eXtremeAir CPC hand dryer
The eXtremeAir CPC is a new innovation in the hand dryer market, this product contains a Cold Plasma generator that effectively creates a reaction from the moisture on the hands and in the air to form hydroxyl radicals that break down the molecular structure of bacteria and small viruses present on the hands, in the immediate surrounding air and surfaces. The eXtremeAir CPC has a completely adjustable motor and heat settings hence why it is included in this discussion.
On maximum speed the dryer tested at a relatively high 86 dB(A) with hands in the airflow, however it reduced to just 73 dB(A) on the lower setting. It is worth noting that at the lower dB (A) level it still had a motor speed of 14,000 rpm and airflow comparable, if not a little faster with the Dryflow Classic PLUS, so with this hand dryer you can find the balance to suit. The eXtremeAir CPC uses as little as 0.3kw on minimum motor speed and only 0.5kw on high motor speed. When you need it to be quieter, you can reduce the motor speed down and add heat. The issue of heat creating bacteria is negated by the cold plasma. Cold plasma is also self-sanitising in the sense that it continuously sanitises the surface of the hands, surrounding surfaces and inside the dryer, so we can say with assurance that the product remains as hygienic 5 years into its life as when it was first tested.
The eXtremeAir CPC is a genuine breakthrough in the market and we believe can be evidenced as the best current solution that can be described as potentially quiet, very hygienic (more so than any other method of drying in fact), very fast and energy efficient. It is also guaranteed for 6 years and highly vandal resistant so we think ticks all the boxes.
For more information on any of the hand dryers discussed please view the website or call +44 (0)114 3540047