1. Can I Disinfect And Reuse The Foam Eartips?

No. Hard, non-porous objects and surfaces are the best candidates for disinfection. Unfortunately, insert eartips are neither. They are porous and soft and do not disinfect well. More importantly, if they are soaked in a solution, the solution is almost certain to stay within the tips thus posing a health hazard to the person who uses it. This is particularly true if someone soaks such a tip in glutaraldehyde (Cidex, Wavicide). The residual glutaldehyde is toxic to the person who receives this tip in the ear.
Bob Kemp, Oaktree Products, Inc.

2. Can I Use The Foam Eartips On Several Patients Before Discarding Them?

No. Insert eartips were designed to be a single-use item, thrown away after each use. Items like insert eartips can become contaminated by the ear or the hands, and can present a health hazard to the next patient, particularly those with diminished immune systems. Audiology patients often have weakened immune systems due to age, underlying disease state (diabetes, HIV) or drug treatment (chemotherapy). Ubiquitous organisms passed from person to person via insert eartips can cause opportunistic infections. Insert eartips should always be thrown away after a single use. Supporting research is as follows:

a. Breathnach, Jenkins and Pedler (1992) found that 26 of 29 stethoscopes were contaminated with staphylococci, and concluded that stethoscopes were a vector for staph infections.
Breathnach, A.S., Jenkins, D.R. & Pedler, S.J. (1992) Stethoscopes as possible vectors of infection by staphylococci. British Medical Journal, 305:1573.

b. Brook (1985) evaluated airline headsets worn by 20 male passengers and found them to be contaminated with staph aureus, staph epidermis, streptococci and corynebacterium. This study led to airlines using disposable headphones and better disinfection of headphones.
Brook, I. (1985) Bacterial flora of airline headset devices. American Journal of Otolaryngology 6:111-114.

c. Bankaitis (2000) examined in-the-ear hearing aids and found that ten of ten were contaminated with bacteria and fungus. While most of the bacteria found on the hearing aids were of the varieties normally found in the ear, some were not normally found in the ear, like fecal-born bacteria. This demonstrated that items that come in contact with the ears can become contaminated by the ear or by the hands.
Bankaitis, A.U. (2000) Hearing aid infection control (IRB #10679) submitted for publication. St. Louis University, St. Louis, MO.

3. Do I Have To Calibrate Insert Earphones, Or Can I Just Plug Them In And Use Them?

Insert earphones should always be calibrated prior to use. Insert earphones were originally designed to "mimic" the response of TDH headphones. Over time, TDH headphones get banged around, and due to normal wear and tear, it is highly likely that they've "drifted" from their original performance over the years. When equipment is regularly calibrated, this isn't a big problem, since any "off-spec" responses can be compensated for by adjustments to the internal board of the audiometer. However, over the years, these changes can add up, and the ER-3A's assume "original integrity" of the TDH phones--so if they're just plugged in and not calibrated, you might get results that differ from the TDH headphones.

For ER-3A insert earphones, there will typically be a 0-5 dB correction at frequencies at and below 4000 Hz, and slightly larger corrections at 6000 and 8000 Hz. If you use TDH headphones as the default, remember to have the insert earphones calibrated at your annual calibration. Many clinicians have their audiometers calibrated for insert earphones as the default and use correction factors for their TDH headphones. A nice feature on some newer audiometers is having both types of earphones selectable, so that either TDH headphones or insert earphones can be used on a patient-by-patient basis without plugging and unplugging the desired earphones.