NOHMI BOSAI LTD.
7-3, Kudan Minami 4-chome, Chiyoda-ku, Tokyo 102-8277 Japan

PHONE :(81) 3-3265-0231
FAX:(81) 3-3265-5348(TRANSLATION)
February 2014
To whom it may concern,
NOHMI BOSAI LTD.
Affection of Discharge Sound of Gas Fire Suppression System on Precision Instruments(Hard Disk Drives and Others) and Countermeasures
The paper entitled “Study of the affection of the sound environment on precision instruments” waspresented during the Annual Meeting of the Architectural Institute of Japan held on September 11,
2010. This paper suggests that the sound environment (particularly, sound pressure when gas isdischarged) may likely affect a hard disc drive (“HDD”).
As this phenomenon is a problem which is beyond expectation and based on newly discovered
knowledge, it does not impair gas fire suppression systems’ compliance with administrativerequirements. However, we think that this phenomenon should be considered as one of the factors
to be reviewed at the design stage, along with fire suppression performance, life safety, preservationof customers’ property and environment together with those concerned (customers, building
contractors, facility managers and the like) on each occasion.
Please review our proposed countermeasures stated below if you think that a countermeasureagainst the above-mentioned gas discharge sound is required in your facilities.
1. Summary of the paper* presented during the Annual Meeting of the Architectural Institute of Japan(1) A sound pressure of 110 dB (not equal to the sound pressure at the HDD location) has caused
a change in the data transfer rate of a HDD under the test conditions of the simulation test
equipment.
(2) The sound pressure level of N2 gas fire suppression systems exceeds 130 dB at a maximum.
For details, please refer to the papers “Study on the affection of the sound environment on
precision Instruments (Part 1, Part 2 and Part 3)” (Doc. Numbers: 40126, 40127 and 40128)【Available from the websites of the National Institute of Informatics (only in Japanese),
Downloading:Not free of charge】: http://ci.nii.ac.jp/naid/110008114240, http://ci.nii.ac.jp/naid/110008114241,
http://ci.nii.ac.jp/naid/110008114242【Available from the websites of NOHMI BOSAI LTD. (only in Japanese), Browsing:Available,Printout: Not available】: http://www.nohmi.co.jp/product/nn100/ronbun.pdf
1PHONE :(81) 3-3265-0231

NOHMI BOSAI LTD.
7-3, Kudan Minami 4-chome, Chiyoda-ku, Tokyo 102-8277 Japan

FAX:(81) 3-3265-5348

2. Proposed Countermeasures(1) Sound insulation and vibration isolation for a HDD housing rack (Use of acoustic
absorption materials and vibration-proof materials, etc.)(2) Measures to protect a HDD before starting gas agent discharge (HDD stop, evacuationof magnetic head, etc.)(3) Improvement in sound-proofing of a HDD itself and/or data protection(backup of data,etc.)(4) Reduction of gas discharge sound(5) Others
With regard to “countermeasure (4) (Reduction of gas discharge sound)” above, Nohmi Bosai
Ltd. (“NOHMI”) can supply new sound reduction type gas discharge nozzles for Nitorgen (N2) gas
suppression system and Halon 1301 gas suppression system (Manufacturer: Koatsu Co., Ltd.).
The performance of the new sound reduction type nozzles is as shown in the table below.
Sound Pressure Level
Flow Rate of (Frequency: up to 100kHz)
Type of Sound Reduction NozzlesNozzles＊2For Nitorgen gas
Ceiling mounting type90 m3/min
97dB
suppression system
90 m3/min
99dB
Side wall mounting type ＊1
For Halon 1301 gas
Ceiling mounting type5kg/sec
96dB
suppression system
7kg/sec
98dB
Side wall mounting type ＊1＊Remark 1 : The above indicated nozzles are typical ones, and oher nozzles having different flow
rates are also available.
＊Remark 2

DischargeNozzle

1m

45° 45°1m

Sound pressure level was measured at these points
1m away from the nozzle.

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NOHMI BOSAI LTD.
7-3, Kudan Minami 4-chome, Chiyoda-ku, Tokyo 102-8277 Japan

PHONE :(81) 3-3265-0231
FAX:(81) 3-3265-5348

Please note that our new sound reduction type gas discharge nozzles are intended for reducing theaffection of the gas discharge sound on a HDD by reducing the gas discharge sound and NOHMI
does not guarantee the performance of the HDDs. In addition, even if a customer replaces theexisting nozzles with the sound reduction type as in the above countermeasure (4) and adopts all ora part of the above countermeasures other than (4), NOHMI does not guarantee the performance ofthe HDDs.
Further note that as the gas fire suppression systems other than N2 and Halon 1301 gas fire
suppression systems would make a loud gas discharge sound, it is expected that precision
instruments, such as an HDD, would suffer certain affection therefrom.
3. Others
The papers in the above paragraph 1 are available only in Japanese. As similar information is alsoavailable in the website of Bvfa (Bundesverband Technischer Brandschutz e.V.), please refer tothem.
In addition, NFPA75 “Protection of Information Technology Equipment” states that power supply to all
the electronic devices should be cut off at the same time when the gas fire suppression systemstarts discharging the gas agent.
If you have any questions regarding this guidance, please contact international division, NOHMIBOSAI LTD. (PHONE: (81)3-3265-0231 E-MAIL: kouhou@nohmi.co.jp)

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