INTRODUCTION TO ASYCUDA++ Ó UNCTAD - SITE (V1.15) 1.16 Lighting Different  types  of  light  are  necessary  for  different  types  of  task.  The  major  types  of  task  involved with computer operations are shown below. Types of Task a)     Data Preparation - little use of screen during keyboard input; b)     Word Processing - moderate use of screen for layout and editing; c)     Interactive - reading screen presented data, manipulation of data. Artificial Light Systems Type a) and b) require higher levels of artificial light than type c), which can be performed within normal office light. Natural light Natural light can cause the lighting level to exceed desirable levels. Glare and reflection These can impair vision and cause visual discomfort so reduction is very important. This may be done by maximising use of non-reflective surfaces, by careful positioning of equipment relative to natural light sources and by use of screen filters. Maintenance Fluorescent tubes must be replaced before flickering becomes disturbing. Space Additional space should be allowed for communally used equipment. Where the workstation is user specific  additional  space  should  be  allocated  only  if  additional  furniture  is  required.  For  ease  of access for repair and maintenance an ideal area of 4 square metres should be allowed. Temperature, Humidity and Dust Equipment will work satisfactorily in a normal office environment. Any extremes of temperature and humidity  that  will  affect  both  equipment  and  users  should  be  avoided.  Computer  equipment  will raise   temperatures   and   may   require   mechanical   ventilation.   Excessive   draughts   can   cause operator fatigue and should be avoided. Low Humidity can give rise to static discharges between the earthed framework of the equipment and the operators. Anti-static devices or humidifiers can be used to minimise this problem. Dust can seriously affect disk drives and build-up can cause overheating leading to system failure. Power supply Normal  office  main  electrical  power  is  usually  adequate  but  a  separate  clean  supply  will  avoid system failures arising from power fluctuations. In some cases separate "smoothing" equipment or UPS machines with backup diesel generators may be needed. Earthing - Mains plugs should be fitted and should be correctly earthed for added safety. Radiation and radiated interference  -  Radiation from equipment is negligible and is much lower than is given off by many household appliances.