Security lighting can be used alongside other security systems to improve their efficiency – especially with CCTV – but in other instances it performs in a standalone role.
However, with the current demands to minimise pollution of the environment, the security installer now has a greater responsibility to actively address the effects of light pollution and to more seriously consider the need for effective energy management.
Certainly we are all alert to the discomfort of unwanted sound. Most of us also have a tale to tell with respect to light trespass from wrongly installed luminaires that create a bad effect on adjacent buildings and neighbourhoods.
Sadly, as security lighting has developed alongside mainstream illumination, a serious problem has been created by light pollution. Indeed it has reached a stage at which it is considered by some observers who have been affected to be as offensive as noise, smoke and chemical discharge.
In practice, it is generally the result of poorly designed lighting systems and inaccurately sited and aimed luminaires. This causes the lighting to spill over and trespass into areas in which it is not intended, including the night sky. Unfortunately, many badly specified security lighting installations have exacerbated the situation and tarnished its image.
Security lighting's role
In general, security lighting systems are energised on demand from automatic sensors or kept illuminated for longer time spans by means of low energy luminaires in conjunction with photocells or timers. CCTV systems have, in the main, been supported by low energy discharge lamps or by integrated infrared lamp techniques.
The benefits of such IR lighting are apparent.
It is invisible to the human eye but visible to monochrome cameras. Therefore it has never been capable of producing a nuisance effect.
It seems there is an increasing acceptance of all forms of pleasing low energy illumination with its inherent reassuring effects but at the expense of demand lighting.
Although the tungsten halogen floodlight and projector has long had a role to play in security, it has also been the greatest offender in creating nuisance effects when incorrectly sited. The switched PIR tungsten halogen unit is now actively targeted for removal from the official Police 'Secured by Design' list.
With this in mind we can look forward to how the future of security lighting networks will surely alter now that environmental issues are at the forefront of all energy using activities.
To reduce light overspill we should introduce more luminaires with directional beams … good at ensuring shadows are not cast close to monitoring points which can provide cover for an intruder
In the first instance, though, we must overview the security lighting that we would specify in relation to the level of risk and probability of attack or danger. We can then determine how we may continue to satisfy the particular classification but take into account the minimising of light pollution and still allow colours and forms to be distinguished. Allied to this there is the need to select the correct light colour appearance and ways in which stray light can be avoided.
Levels of risk
Low risk security
Standard luminaires provide safety lighting and allow a reasonable level of security to be achieved. Sensors or photocells are mounted at the manufacturer's recommended heights.
Mid risk security
Luminaires are employed that have an increased resistance to vandalism together with sensors or photocells that are not normally accessible to vandals/criminals. Protection is given to the mains supply and the employment of multiple luminaires to account for lamp or component failure.
High risk security
Vandal resistant luminaires and sensors or photocells/timers that are inaccessible are used. Multiple luminaires and wiring networks cover the greater risk category. All cabling and the mains supply should be protected and different supply phases used. Systems require monitoring and links with the outputs of other security systems including CCTV.
Lighting pollution has come to the forefront for a number of reasons. It spoils the natural effect of the night skies, creates a nuisance effect and the greater the light pollution the greater is the power consumption. Therefore, to save the environment we must think more in terms of focusing on the minimum lux levels required. In addition, we must move away from high energy levels and consider more applications using low energy new generation luminaires.
Some light pollution unavoidable
It is accepted with modern luminaires that both aesthetics and perception are heightened. In order to reduce light overspill we should introduce more luminaires with directional beams.
These are also good at ensuring that shadows are not cast close to the points being monitored so that a cover is not provided for an intruder. They also exhibit a more pleasing light form to better guide authorised persons through an area.
Unfortunately there must be some light pollution in order to satisfy safety and security applications, so the answer lies in a compromise. Nevertheless, by introducing measures to combat light pollution we become conscious of energy management.
With internal applications, any lighting more than ten years of age should have the luminaires upgraded. Refurbishment programmes can produce 60 per cent energy savings and reduced maintenance costs. Old floodlighting and high wattage light bulbs (300 W to 1500 W) should be replaced with high pressure SON units as these are energy efficient and provide satisfactory colour rendering.
For low mounting heights they are best replaced with new generation fluorescent fittings with modern louvered or high performance prismatic lenses. However, it is the subject of outdoor applications to which the greatest attention must be made. If incandescent high wattage filament lamps are being used over extended periods of time these are best replaced with compact fluorescent luminaires or SON high pressure lamps.
Alternatively, the cool white form of mercury fluorescent or metal halide discharge lighting can be employed if superior colour definition is important. In addition to providing energy savings in the order of 60 per cent, a superior less harsh light form would also be introduced. This means that tungsten halogen floodlighting would become dated in many instances.
For applications in which the installer believes that tungsten halogen demand lighting still has a role to play they should be replaced by 150W versions in mini-enclosures
For those applications in which the installer believed that tungsten halogen demand lighting still had a role to play they should certainly be replaced by 150W versions in mini-enclosures wherever possible.
Relating energy management and light pollution to the security risk, be it low, mid or high we can then make our observations.
Low energy lighting
For low risk security areas – particularly domestic applications – there is a case for the use of low energy lighting using modern compact fluorescent luminaires in preference to demand lighting if it is to be used over long periods of time. Compact fluorescent has a small light source and matches filament lighting in colour and quality but is more energy conscious. Photocells can be used as a replacement for automatic sensors or timers may be interfaced in the system. Low energy lighting also generates a reassuring effect on approaching the premises since illumination is already available.
Controlled and contained
In mid risk security applications, floodlighting is easily achieved by extended period discharge lighting such as SON, mercury fluorescent or metal halide with its inherent low running costs. Directional floodlights are available so that the area to which the illumination is projected can be both controlled and contained. These units use flat glass panels and special optics to define the light paths and cut off the areas that cause light trespass and spill.
They also achieve good rendering so that adequate images may be captured on CCTV systems. Mounted at a high position, they are protected from damage so fulfil their security function. The photocells can also be mounted at a high elevation at almost any point so they are equally well protected.
If the specification is unable to support the use of floodlighting, an option is to employ anti vandal flush mounted luminaires that are mounted in walls by means of recessing boxes with the lamps held behind vandal resistant louvres.
These feature toughened glass and are high impact with the lamp and control gear held some distance back from the louvre so that any impact cannot be transmitted to the lamp or control gear. Any shocks being absorbed by the surrounding building structure. These luminaires cause no light overspill because they are mounted at a low elevation allowing illumination of an exact and clearly defined area only.
Protected operation
In high risk security environments we can continue to employ similar techniques to those associated with mid risk but use different electrical phases or additional phases to account for supply failure together with multiple luminaires at various elevations. The cabling must also be protected and monitored and be supervised by the other security system networks. Depending on the sensitivity of the area every luminaire may not be required at all times but can be energised on failure of the other lighting in the protected area. Central inverters can be used to support the system to cater for power failure or any spare capacity in an existing emergency lighting network can be utilised.
A future perspective
Security lighting must respond to the changes required of it if it is to be innovative, develop alongside other technologies and fulfil environmental demands.
We do not wish to see it living in the past. Therefore it must reflect the needs of energy management and other higher quality measures that are sweeping through our industry.
Source
Security Installer
Postscript
* Gerard Honey is an installer and writer of industry textbooks including:
Electronic Protection and Security Systems; Electronic Access Control and Electronic Security Systems Pocket Book (all published by Newnes).