1. Earmuffs or over-ear protection cannot be used – HMT-1/HMT-1Z1 occupies all the space above the ears where the earmuffs would seal out the noise. HMT-1/HMT-1Z1 also utilizes the helmet mounting slots where earmuffs typically attach. Earmuffs will prevent the user hearing the remote mentor talking to them. Earmuffs with speakers inside and a 3.5mm plug will not be intrinsically safe when plugged into HMT-1Z1, even if they are separately Intrinsically Safe certified/compliant. (They have to be certified together.)
  2. RealWear has NRR headphones 33dB SNR/NRR, Intrinsically Certified to C1/D1, ATEX Zone 1 when used with the HMT-1Z1. Memory foam tips in small, medium and large sizes are available as a consumable item. This product has been optimized for HMT-1/HMT-1Z1 use including its cable lengths and connectors.
  3. If the user is trained on fitting the earbuds properly, he/she can get 33 dB NRR actual performance. To account for user error in fitting, NIOSH recommends de-rating in-ear buds by 50%. The worst case NRR performance in the real world is 16.5 dB
  4. The hearing damage limit for continuous exposure is 85dB (NIOSH). 85dB+16.5dB= 101.5dB. This is louder than the limit of voice recognition working on HMT-1/HMT-1Z1 (which is rated at 95 dB). If it is louder than 101.5dB for continuous exposure the user will not be using the HMT-1/HMT-1Z1.
  5. The NIOSH one-hour hearing damage limit is 94dB. 94dB+16.5dB = 110.5dB. Areas greater than 110.5dB where the user spends greater than or equal to 1 hour at a time are extremely rare in the workplace.
  6. In practical terms our NRR headset fulfills hearing safety needs in all situations where the HMT-1/HMT-1Z1 is applicable for use.