- In this Q and A video,
we are going to answer the question,
"What is high risk task area emergency lighting,
and how do you provide it?"
Now, just before we explain the answer to this question,
please be aware that this video is one of a series
that we've made on the subject of emergency lighting
in association with Robus.
They can be viewed individually
or you can click the link in the description below
to view them as part of a free online training package
to help you with your CPD,
and you'll receive a certificate
to prove that you've completed the course.
High risk task area lighting is very neatly defined
for us in the "Electrician's Guide to Emergency Lighting."
In the definition section, it states that this kind
of lighting is, "that part of emergency escape lighting
that provides illumination for the safety
of people involved in a potentially dangerous process
or situation, and to enable proper shutdown procedures
for the safety of the operator
and other occupants of the premises."
A classic example of this might be a kitchen
where you've got open flames,
sharp knives being used close to people's fingers,
pots of scalding liquids,
and a fairly high pressure intense environment.
Of course, this is just one example.
Other places might be workshops in industrial settings
or manufacturing environments.
One often overlooked area is in control rooms
where machinery and processes are controlled from.
While that space may not present a high risk in itself,
it's critical the lighting remains at a sufficient level
to allow the shutdown processes to take place
in order to prevent danger elsewhere.
In all these places, if the regular lighting is lost,
then it's essential to maintain people's safety.
Notice in the definition,
the thought that part of the reason for this type
of lighting is to allow shutdown procedures to take place.
So this type of lighting is not designed
to keep people working while the main lighting is off.
First of all, we need to figure out how to identify
where in a building would need to be classified
as a high risk task area.
This is done by carrying out a risk assessment,
which should be done for the building as a whole,
but the same process applies to high risk areas as well.
The Society of Light
and Lighting suggests the following process,
"Identify potential fire hazards in the workplace,
sources of ignition, fuels, work processes.
Identify the location of people
at significant risk in case of fire,
who might be in danger, employees, visitors,
and why.
Evaluate the risks.
Are safety measures adequate or does more need to be done?
Fire detection, warning, means of fighting fire,
means of escape, fire safety training of employees,
maintenance and testing of fire precautions.
Carry out improvements, record findings and actions taken,
prepare emergency plans,
inform, instruct, and train employees.
Keep assessment under review,
revise it when situation changes."
In addition to this, the Industry Committee
for Emergency Lighting or ICEL,
part of the Lighting Industry Association,
have published a technical statement
highlighting the importance of collaboration
between various bodies and individuals
when producing the fire risk assessment.
The fire risk assessor should take on board information
from the user or duty holder for the building,
requirements from the insurance,
requirements from building control and legislation,
and also very importantly,
fire protection system supplier.
If you look at the box
in the image depicting this information,
you can see that includes emergency lighting
and sign suppliers.
If the risk assessment identifies areas
that would require high risk task area emergency lighting,
then those areas will need to comply
with very specific requirements.
These can be found in BS EN 1838
and are summarised for us under subheading 4.6
of the "Electrician's Guide to Emergency Lighting"
as follows.
"A, in areas of high risk,
the maintained luminance on the reference plane shall be
not less than 10% of the required maintained luminance
for that task.
However, it shall be not less than 15 lx.
It shall be free of harmful stroboscopic effects."
Okay, so let's break that down.
The starting point for this requirement
is the reference plane.
When lighting design is carried out, it's important to know
where the light levels are being measured.
For corridors, it's usually the floor.
If you're designing lighting for a classroom
or an office, you'd probably think about the light levels
at desk height and so on.
This area that you measure the light on is referred to
as the reference plane.
For high risk task areas, it's literally all about the area
where the high risk task is taking place.
So if it was an industrial kitchen,
you might set the reference plane on top of the gas burner
and over any workstation nearby.
This would allow for the safe shutting down of the flames
and removal to a stable surface
of any hot pans and sharp knives.
So on this reference plane, the average illuminance
or how much light is falling on that area should be at least
10% of the illuminance level required for that task
when the lighting is working fine, if not more.
So using our example of a commercial kitchen space,
the recommended lighting level will vary
depending on the exact circumstance,
but a common value found
in the "Guide to Lighting" is 500 lx.
So in an emergency situation,
the lighting level on the task area would need
to be at least 10% of that value,
so 50 lx.
The requirement continues to state
that the illuminance level should never be less than 15 lx
in a high risk task area.
So if a task required 100 lx under normal lighting levels,
applying the 10% rule would not be acceptable
as this would bring the emergency lighting level
to 10 lx.
It would still need illuminating to at least 15 lx
to comply.
Interestingly, this information is repeated
in the "SLL Guide to Lighting,"
but elsewhere in that document,
it seems to contradict itself.
It states that the required emergency lighting level
in a kitchen should be 15 lx on the reference plane.
So how to understand this seeming discrepancy?
Well, it makes sense if you view the two pieces
of information as complementary.
In a kitchen, there's lots of different tasks going on
with different levels of risk involved.
So while the 15 lx value would be okay
in lower risk areas in the kitchen,
for the specific higher risk tasks,
you'd apply the more stringent value.
We'll find a similar situation in a moment when we discuss
how long the emergency lighting should stay on for.
The next requirement is "B, the uniformity
of the high risk task area lighting illuminance shall be
not less than 0.1."
So we're still looking at the reference plane here
and the specific values for uniformity.
Uniformity is all to do
with how evenly spread out the light is.
If you have a single light source in a room,
this will usually cause a bright spot directly below it,
and then the level will drop off
as you get further away from the source.
If you have more than one light source in a room,
then the picture becomes a little more complex,
but you will still have points in the room that are brighter
and some that are dimmer.
The type of uniformity in this requirement is found
by taking the lowest illuminance value
on the reference plane
and dividing that by the average illuminance.
This value will always be between zero and one.
The closer to one, the better the uniformity.
So the requirement for uniformity of 0.1
or above here should not be too difficult
to achieve across a task area reference plane,
and is likely to be achieved
with the use of a single fitting.
Next up, we get a requirement that might not be as familiar
as some of the information we've looked at so far.
It reads, "C, disability glare shall be kept low
by limiting the luminous intensity
of the luminaires within the field of view.
These shall not exceed the values in Table 1,
or table 4.2 in this Guide,
within the zone 60 degrees to 90 degrees
from the downward vertical at all angles of azimuth."
Okay, so again, let's do some more picking.
We've got here a reference to disability glare.
This doesn't have anything to do with people
who have accessibility issues with their site,
but rather it's defined in the "SLL Lighting Guide"
as "glare that impairs the vision
of objects without necessarily causing discomfort.
Disability glare can be produced directly or by reflection."
So it's referring to the disabling effect
that glare could have on someone trying to carry out a task.
Glare is simply the measurement
of how bright a light source is
compared with its surroundings.
This would be a problem at night
or in a room without any natural light
if the lighting was to fail
as the emergency sources would sit
against a very dark background,
meaning that it could cause the human eye
to effectively overload
and make it difficult to see what they're doing.
Not good in an emergency situation in a high risk task area.
So, glare needs some consideration.
It goes on to add that the glare values "shall not exceed
the values taken from table 4.2 in the Guide."
In the right hand column,
we see the maximum values in luminous intensity
we are allowed with fittings mounted at different heights.
Now, notice though the additional requirement in indent C.
It states that "these values are only applicable in the zone
60 to 90 degrees from the downward vertical."
So you can see on this diagram
that it only applies within this zone.
The reason for this is that glare varies
depending on where you're standing in relation to the light.
If you are under a light source staring straight up at it,
then you're going to get glare.
It can't be avoided.
So this restriction only applies
within those areas that we've shown on the diagram.
It also adds to the comment
about this applying "at all angles of azimuth."
This just refers to the horizontal angle
you're viewing it from.
So wherever you stand around the fitting,
the restriction to glare applies.
The easiest way to make sure that you get this right
is just to talk to the manufacturer of your chosen fittings.
You'll often find they're manufactured to comply
with this requirement anyway.
Failing that, you can calculate glare
on a piece of free software like Vilux or Relux.
The next requirement is found in indent D and reads,
"In order to identify safety colours, the minimum value
for the colour rendering index R-A of a lamp shall be 40.
That luminaire shall not substantially subtract from this."
This is just a measure of how well
a light source shows the true colour of an object,
and with most modern LED emergency light sources,
they all have values well above 40,
which is not a spectacularly difficult value to achieve.
Then, indent E refers to, "The minimum duration
shall be the period for which the risk exists
as agreed with the duty holder or responsible person."
Again, we find this curious seeming contradiction
in the "SLL Guide to Lighting" under subheading 3.2.1.3
on high risk task areas.
We find similar direction
that minimum duration is "the period
for which the risk exists to people."
This makes sense in both documents
because if you set a blanket arbitrary minimum duration
that the emergency lighting is on for,
you run the risk of that either not being long enough
or much longer than is needed.
However, we also find this direction later
in the document in table 3.4
where we have the direction about minimum illuminance.
It shows that for kitchens and other areas,
we would need the specific value of 30 minutes.
So which is it?
30 minutes or the time period for which the risk exists?
Well again, view them as complementary directions.
If you aim for 30 minutes
and the risk period is shorter than this,
then you've built in a safety factor.
And if the risk period is longer than 30 minutes,
then use that value instead.
It's hard to go wrong
if you go for the more stringent requirement.
The rise of the LED as the most common light source means
that it's much easier to achieve long periods
of emergency illumination anyway.
Finally, we come to indent F.
"High risk task area lighting shall provide
the full required illuminance permanently
or within 0.5 seconds depending upon application."
Now, this is a bit of a throwback to the old days
of emergency lighting when we were using fluorescent lights
instead of LEDs.
There could be a period of time,
especially on non-maintained fittings,
when it would take a while for the tubes to warm up
and achieve full brightness.
Or if the emergency lighting was fed
from a backup generator, it could take even longer
for the lights to come on.
In a high risk task area, the lights being off
even for a few seconds could be disastrous to both people
and processes.
So this regulation was used to reduce this period
that it could be off for.
Again, though, with the transition to LEDs,
it's become pretty easy
to achieve very short transition periods,
even on standard fittings.
So there we go.
That's what we mean
by high risk task area emergency lighting
and how we provide it.
But you may be wondering what the legal requirements
for individuals are for emergency lighting.
Well, to find out more about that,
check out this video right here,
or click the link in the description below to watch it
as part of a free training package to help you with your CPD
and you'll receive a certificate as well.
For further information on emergency lighting from Robus,
check out their latest catalogue
or get in touch with them via email on info@robust.com.
All that remains in this video is to say thank you very much
for watching.