Dust and Particulates Dusts are formed by the mechanical breakage of a parent material, down into smaller particles, usually larger than 0.5 microns. Dusts can be formed by: Drilling Crushing Grinding Sanding Milling Sweeping The smaller the dust, the longer it hangs in the air and the easier it is to inhale. Other forms of particulate: Mist, Weld Fume, Smoke, Aerosols, Fibres etc
Introduction Limitations of the respiratory system’s defences… Our defence mechanisms have problems with the following: Large quantities (Can swamp our defences) Toxic, poisonous or infectious particles (Can damage our lungs as well as other parts of the body) Sensitising particles (Can trigger allergic reactions e.g asthma) Very small particles (Can bypass most of our defences to reach the lungs)
30 – 5 µm diameter particles are filtered out here 5 – 1 µm diameter particles are filtered out here Particles less than 1µm diameter can reach the lungs Introduction Filtration by the respiratory system
Hierarchy of controls Most effective Least effective NIOSH Workplace Safety and Health Topic, CDC Hierarchy of Controls, www.cdc.gov/niosh/topics/hierarchy
Respiratory Protective Equipment (RPE) Tight-fitting filtering respirators Powered filtering respirators Supplied air respirators Breathing Apparatus (BA or SCBA)
How do Particulate Filters Work? Polypropylene Blown Microfibre Filter
Mechanical filtration… filter fibres Advanced Electret Filter Material Filter fibres • Gaps between filter fibres are larger than the particles • Filtration relies on particles making contact with filter fibres ? What’s stopping the particles from bouncing off the filter fibres
Mechanical filtration… filter fibres Advanced Electret Filter Material Filter fibres • Once a particle touches a filter fibre it will be held there quite firmly by Van der Waal’s forces What’s stopping the particles from bouncing off the filter fibres ?
Assigned Protection Factors Disposable Respirators Protection Levels FFP1: Particulates up to 4x WEL FFP2: Particulates up to 10x the WEL FFP3: Particulates up to 20x the WEL* FFP1 = APF 4 FFP2 = APF 10 FFP3 = APF 20 *Workplace Exposure Limit – see HSG 53
These all work on a basic principle? • Negative pressure principle • Requirement to be Face Fitted • Must seal well to face or inward leakage of contaminated air reduces protection
What is fit testing? • Means of assessing how well a respirator seals to a face • 2 main methods are used: Qualitative taste test Quantitative test using Portacount
Quantitative Particle Counting Test • May be used for disposable respirators, half masks and full-face masks with particle filters. • Uses TSI Portacount. • Facepiece must be probed. • Compares particle count inside and outside facepiece. • Result reported as a fit factor
Fit test methods – Qualitative Taste Test • For disposable respirators and half masks with particle filters. • Pass or a fail. • Works on the principle of taste. • A mist is directed into a hood • If there is a leak at the face seal the wearer will taste the solution and fail the test.
Fit Testing Exercises 1 min for each exercise = 7 Minutes
However not everyone can create a Seal? • Facial Scarring • Adventure Sports ??? • % of the population • Beard Wearers
Respirators not requiring fit testing • Respirators that rely on air flow through the head top and have a loose fit to the face e.g. helmets and hoods – loose fitting