Dear Ladies and Gentlemen,
In this article, we would like to inform you about the latest findings in the area of hearing aid drying.
Sweat, moisture and cerumen initially adhere to the hearing systems on the surface. Through a capillary effect (cohesion and adhesion), the mixture enters the interior of the hearing systems and accumulates there. The cocktail of salts, acids, organic components and water leads to failures and expensive repairs, including total loss.
The silica gel dry capsules or tablets absorb humidity as well as hearing aid moisture. Drying depends on the net salt content (g), the temperature (°C), the relative humidity (%) and a small and airtight drying box in terms of volume. The disadvantages are the barely visible wear process of the tabs, the continuous replacement of used tabs, chemicals and environmental aspects.
Drying by convection of warm air is the most common way of drying hearing aids over many years. It requires the largest possible temperature difference between the drying chamber (Ti) and room temperature (Ta). Older hearing aids were tested with an upper limit temperature of 60°C. and dried at approximately 50°C. This is a very effective method of drying, especially for battery-operated hearing systems, where the batteries can be removed during drying.
Hearing aid manufacturers specify a maximum temperature of 40°C for the increasingly delicate hearing systems and the increasing number of rechargeable hearing systems with lithium batteries. With this low temperature difference, convection drying is uneconomical because it requires a very long drying time.
In the hearing care sector, lithium-battery hearing systems and company-specific charging stations have become established. Charging stations with an all-round function are new and critical at the same time. This means charging stations that promise 1st charging 2nd network-free recharging with LiPo battery, 3. drying and 4. hygiene in the smallest installation space. The idea is good but unfortunately points 3. and 4. work only insufficiently or poorly in practice. In many cases, the heating of around 40°C that occurs during battery charging is communicated as heating or drying, which is completely unsuitable for practice in the absence of convection without supply and exhaust air channels or even when the lid is closed and can cause moisture damage to the hearing system.
Furthermore, without venting, this temperature is the perfect breeding ground for germs and bacteria. This can significantly increase the risk of ear infections. The 275 nm UV LEDs, which are mostly used for hygiene, cannot reach the entire hearing systems in the charging slot and therefore cannot guarantee sterility of 99.9%. Wavelength, intensity and, above all, radiation geometry set physical limits here.
One of the most efficient and gentle drying processes is drying by a strong airflow generated by a high-performance fan. Around 5 cubic meters of air flow around the hearing systems per hour. The basis for drying with swirled air flow during assembly is the vapor pressure gradient of the liquid. Not only is the moisture adhering to the outside evaporated, but efficient interior drying is also achieved at the interfaces of the hearing systems via water vapor partial pressure compensation.
This turbo drying combined with effective UV-C light (253.7 nm) ensures perfectly dried and hygienically cleaned hearing systems. This protects the hearing systems, ensures their use and maintains the joy of hearing.
Your flow-med team
