HP Server rp7400 Generic Site Preparation Guide - Edition 6 - Page 24

ESD Prevention, Humidity Levels Influence the Creation of Static Charges, Relative Humidity

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resistance between connections, leading to equipment failures. High humidity can also have an adverse affect on some magnetic tapes and paper media. CAUTION: Low humidity contributes to undesirably high levels of electrostatic charges. This increases the electrostatic discharge (ESD) voltage potential. ESD can cause component damage during servicing operations. Paper feed problems on high-speed printers are usually encountered in low-humidity environments. Low humidity levels are often the result of the facility heating system and occur during the cold season. Most heating systems cause air to have a low humidity level, unless the system has a built-in humidifier. Be aware when reviewing air quality that temperature and relative humidity can be a factor in corrosive issues. ESD Prevention Static charges (voltage levels) are created when objects are separated or rubbed together. Be aware that destructive ESD levels can exist very far below human thresholds. Extreme caution must be used to protect contemporary microcircuitry that is manufactured densely and physically smaller. The voltage level of a static charge is determined by the following factors: • Types of materials • Relative humidity • Rate of change or separation Humidity Levels Influence the Creation of Static Charges Table 1-2 compares the static charges generated by activities in different humidity levels. IMPORTANT: Use ESD processes and ESD prevention equipment whenever equipment needs servicing. Table 1-2 Effect of Humidity on ESD Charge Levels Personnel Activity1 Humidity2 and Charge Levels (voltages)3 26% 32% 40% 50% Person walking across a linoleum floor 6,150 V 5,750 V 4,625 V 3,700 V Person walking across a carpeted floor 18,450 V 17,250 V 13,875 V 11,100 V Person getting up from a plastic chair 24,600 V 23,000 V 18,500 V 14,800 V 1 Source: B.A. Unger, Electrostatic Discharge Failures of Semiconductor Devices (Bell Laboratories, 1981) 2 For the same relative humidity level, a high rate of airflow produces higher static charges than a low airflow rate. 3 Some data in this table has been extrapolated. For more information regarding ESD, see the HP ESD Standard HP-00005-04 at: http://standards.corp.hp.com/smc/hpstd/pdf/F-HP0000504.pdf Relative Humidity Where possible, maintain a humidity range of 40% to 55%. Static Protection Measures Follow these precautions to minimize possible ESD-induced failures in the computer room: 24 General Site Preparation Guidelines

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resistance between connections, leading to equipment failures. High humidity can also have an
adverse affect on some magnetic tapes and paper media.
CAUTION:
Low humidity contributes to undesirably high levels of electrostatic charges. This
increases the electrostatic discharge (ESD) voltage potential. ESD can cause component damage
during servicing operations. Paper feed problems on high-speed printers are usually encountered
in low-humidity environments.
Low humidity levels are often the result of the facility heating system and occur during the cold
season. Most heating systems cause air to have a low humidity level, unless the system has a
built-in humidifier.
Be aware when reviewing air quality that temperature and relative humidity can be a factor in
corrosive issues.
ESD Prevention
Static charges (voltage levels) are created when objects are separated or rubbed together.
Be aware that destructive ESD levels can exist very far below human thresholds. Extreme caution
must be used to protect contemporary microcircuitry that is manufactured densely and physically
smaller.
The voltage level of a static charge is determined by the following factors:
•
Types of materials
•
Relative humidity
•
Rate of change or separation
Humidity Levels Influence the Creation of Static Charges
Table 1-2
compares the static charges generated by activities in different humidity levels.
IMPORTANT:
Use ESD processes and ESD prevention equipment whenever equipment needs
servicing.
Table 1-2 Effect of Humidity on ESD Charge Levels
Humidity
2
and Charge Levels (voltages)
3
Personnel Activity
1
50%
40%
32%
26%
3,700 V
4,625 V
5,750 V
6,150 V
Person walking across a linoleum floor
11,100 V
13,875 V
17,250 V
18,450 V
Person walking across a carpeted floor
14,800 V
18,500 V
23,000 V
24,600 V
Person getting up from a plastic chair
1
Source: B.A. Unger, Electrostatic Discharge Failures of Semiconductor Devices (Bell Laboratories, 1981)
2
For the same relative humidity level, a high rate of airflow produces higher static charges than a low airflow rate.
3
Some data in this table has been extrapolated.
For more information regarding ESD, see the HP ESD Standard HP-00005-04 at:
Relative Humidity
Where possible, maintain a humidity range of 40% to 55%.
Static Protection Measures
Follow these precautions to minimize possible ESD-induced failures in the computer room:
24
General Site Preparation Guidelines