Laser Safety Flashcards
What are the two primary legislation for health and safety?
Health and safety at work Act 1974 (inspectors, legal duty as far as is reasonably practicable to health and safety of all employees) and the Consumer Protection Act 1987(producers are strictly liable for all defective products). Have to prove that it is safe.
What are three secondary legislations for essential health and safety requirements?
The Supply of Machinery (Safety) Regulations 2008, SI 2008/1597
- laser equipment must be designed and constructed in a way to prevent any accidental radiation
-no health risk should be created by laser radiation
The Provision and Use of Work Equipment Regulations 1998, SI 1998/2306
-Take measures as to reasonably practicable to control hazards
The Control of Artificial Optical Radiation at Work Regulations 2010, SI 2010/1140
-Exposure limit values (ELVs) are set
-must assess risk to eyes and skin
-carry out assessment for laser radiation in regard to above
The General Product Safety Regulations 2005, SI 2005/1803
-no product should be on the market unless the product is ruled safe.
How to assess exposure and risk for control of artificial optical radiation at work regulations?
Measurement/calculation of exposures
* competent services/persons
* suitable intervals
Consider:
* level, wavelength, and duration of exposure
* sensitive risk groups
* interactions with photosensitising chemicals
* indirect effects (temporary blinding, fire, etc)
* multiple sources
* classification (eg class 3B or 4 lasers)
What is the hierarchy of controls for the laser?
Elimination -> substitution(alternate working methods) -> engineering controls -> administrative controls(maintenance and design, restrict duration and level of exposure) -> PPE…. this is from most to least effective.
What is the objectives of BS EN60825-1:2014?
- to protect persons from laser radiation by indicating safe working levels and by introducing a system of classification
- lay down requirements - manufacturer and user - to establish
procedures for the supply of information - ensure adequate warning is given through the use of signs, labels and
instruction - reduce the possibility of injury by minimising access to laser radiation
via protective features and control measures
What are the classification classes determined by for lasers?
Accessible Emission Limit (AEL)
– Is the maximum level of laser radiation that can be
accessed from any product surface.
– This includes leakage radiation as well as main beams
from intended exit apertures.
– Classes take into account: laser wavelength, exposure
duration, viewing conditions
What are the main classes of this module and what do they do?
Class 1 – Practically no exposure to eyes or skin
Class 2 – Visible beams with safe exposure for eyes under certain
conditions
Class 3R – Higher output for specific use (uncommon in materials
processing). Not to view with binoculars or telescopes.
Class 3B – Still skin safe but not eye safe.
Class 4 – Unlimited → Practically all materials processing lasers, no maximum output and fire hazard.
The HIGHER the CLASSIFICATION = GREATER HARM potential
What is laser radiation damage depending on when its to your skin and eyes ? 5
- wavelength of radiation
- type of tissue exposed, eye or skin
- energy or power of the radiation
- size of the irradiated area
- exposure duration
How does intensity and divergence of the beam affect the laser?
A high intensity beam that can be focused, reflections can be hazardous.
Low divergence means the beam spreads out very little over large distances.
What is MPE? and what does it relate too?
Maximum Permissible Exposure. Level of laser radiation below which it is believed no harm will be done to the exposed individual. Applies to the eye and skin, depends on several factors like irradiance or radiant exposure.
What is Nominal Hazard Distance ?
NHD, At some distance, as the beam diverges, the irradiance of the laser beam will equal the MPE
* At greater distances the MPE will not be exceeded
* Laser is a hazard within this distance, and “safe” beyond it.
What are non-beam hazards?
- Hazards associated with a laser or laser product can present a greater
danger than the laser or radiation itself - Non-beam hazards are those other than optical radiation hazards
What are types of hazards defined by?
The way in which it is generated,
– Laser
– Beam Delivery
– Process
– Environment
– People
What are types of non beam hazards?
- Laser associated hazards arise directly from the laser or laser
installation - Beam delivery associated hazards can arise from the mode and
elements which make up the beam delivery system - Process associated hazards arise from the task or application that the
laser is performing - Environment & People. Different applications in different environments
by different people
What are electrical hazards?
- High voltage supplies supplies can be
lethal - Requires trained operators
- Electricity at Work Regulations apply
- High quality installation is critical
What are chemical hazards?
May arise from:
* The active medium of the laser,
eg. fluorine gas for an excimer laser
* Toxic fumes from material processing, laser dyes or solvents used for
dyes, cleaning, etc.
* COSHH Regulations may apply - a risk assessment must be made
What are laser generated fumes in regard to toxicology?
- By-products of material processing can include fumes gases & vapours.
- gases & vapours can react chemically with lungs & respiratory system.
- E.G. stainless steel breaks down into iron chromium & nickel (various
valency states) pose a chemical hazard.
What are the COSHH guidelines for carcinogens?
Maximum exposure limits (MEL), specify the amounts in the workplace atmosphere fume produced from any
process will vary in composition, size distribution, morphology & toxicity
What are the effects of fumes on people?
- Effects dependant upon: fume composition, chemical/biological activity,
how it enters the body, length of exposure & fume concentration - individual species toxicity can be classed as acute or chronic
– acute is short term in hours
– chronic summed over a long period
What do gaseous emission depend upon?
- Depends of the solubility of the gas in blood plasma
- Chemical and biological activity
- High activity gases/high solubility e.g. chlorine attacks upper tracts
- Less soluble gases get into the lungs - alveoli and bronchioles
- Low solubility get into the blood - kidneys & other internal organs
Where should fume extraction be and what filtration should be in place?
- You must know fume composition and concentrations
- Fume extraction must be at point of generation NOT general
environmental - define fume filtration and disposal based upon composition
- disposal agency must know content
What are the mechanical hazards of a laser machine?
- the water installation, poor
location and fittings - gas installations, location and
fitting - water condensation affecting
optics - manual handling of heavy/bulky
laser and equipment
What are optical hazards for lasers?
- open beam arrangements
- fibre optic integrity
- poorly mounted optics
- misalignment problems
- stray reflections and errant beams
Which laser class and what are fire hazards caused by?
- Class 4 lasers present a fire hazard
- Direct beams and reflected beams can cause combustion
- Materials used for beam stops/enclosures must be of suitable
materials
Why use engineering controls first?
- Well designed safety measures incorporated at the outset can improve
effectiveness, efficiency, motivation and monitoring and control - This is achieved through system design and engineering
▪ They will always add control and usability to a product or system
▪ ‘Tacked on safety’ is expensive, less effective and can hinder work which
leads to shortcuts and accidents
Who is responsible for laser processing equipment?
- Primary responsibility lies with the manufacturer to provide safe equipment in accordance with BS EN60825-1:2014
- But the laser user has responsibilities according to the class of laser in use
▪ Remember to include appropriate controls for an embedded laser in a laser product if the classification warrants additional control measures
▪ Ideally a product should be Class 1 or 2 even though it might include a
Class 3B or 4 laser system
What are examples of engineering controls?
- Protective enclosures
- Housings
- Interlocks on housings, lasers, doors, etc.
- Beam attenuators and shutters
- Key switches
- Beam enclosures/stops
- Control of beam path
- Delayed operation switches
- Warning lights, bells
- Viewing or filtered windows
- Alignment aids
What are protective housings and enclosures?
- Placed around a laser by the manufacturer or laser user to prevent access to radiation > Class 1 AEL
- These should be appropriate for the task, fixed with tamper proof fasteners,
interlocked with suitable service panels for service and maintenance
What are service panels and what are their requirements to be effective?
- Should be labelled, interlocked (Class 3B and 4) and fixed with tamper
proof fasteners - The installation should consider those having to carry out service in the
area - why should they be exposed to any increase in optical radiation or
other hazards?
What are interlocks on the laser and what are the requirements for these to be effective?
- Must be tamper proof and fail-to-safe
ie. they must not increase the hazard if
they fail - The status should be clearly
indicated eg. large flags on the defeat
keys & warning status indicators on
operators panels
Interlocking to power supplies - A requirement for some lasers,
preferably only used for emergency shut down - Operational interruption should be
made by external shutters - Restarting lasers ages them
What do beam attenuators and shutters do?
- Class 3B and 4 lasers must have a method to prevent access to
radiation from the laser aperture
– shutters, attenuating filters
What is the key switch and idicator panel for?
Class 3B and 4 lasers require a key switch which render laser
inoperable if removed
– requires correct issue and storage after use
– key can include magnetic
cards, etc
What are emission warning devices for?
- Warning devices either visual or audible to indicate when lasers are on
or capacitor banks charged (Class 3B and 4 lasers) - Devices must be clearly visible even through protective eyewear
- Devices must be suitably located especially for remote control panels
and multiple apertures
What are filtered viewing windows and optics used for ?
- Filtered viewing windows and optics are useful in protecting against
radiation and for monitoring of a process - Can remove the need for reliance upon goggles
- Can range from large scale control rooms to small panels in an enclosure
- Filtered viewing windows are expensive and must still function as
mechanical guards
What are practical issues with lamination and UV degradation protection?
- Lamination is essential to meet
impact and containment issues, we have undertaken considerable testing to ensure integrity of filter after impact - Laminate within a polycarbonate
sandwich - expensive - Laminate single side to either glass
or polycarbonate depending upon
performance expectations - UV degradation tests are good to
simulate lifetime issues - You cannot beat a good steel or
aluminium containment with a cheap
cmos camera - Cost is typically 1/3 of what a room
fortress & goggles solution would be.
What are examples of administrative controls?
- Laser Safety policy;
- Laser Safety Officer (LSO)
- Risk assessment
- Standard Operating Procedures (SOPs) and Written
Safety Instructions (WSI) - Warning signs and labels
- Key control
- Maintenance & service manuals
- Education & training
- Marking of protective devices
- Laser controlled area/restricted access
