IB-3 Hazardous Chemicals - Engineering Controls & PPE

Question 0

How do you measure if the APF = Assigned Protection factor of RPE

What does APF repersent

Answer 0

APF = concentration of contaminant in the environment / OEL

APF represent the level of protection which can be realistically achieved under working conditions if used correctly

Question 1

Outline the tests that could be used to assess the efficiency and effectiveness of local exhaust ventilation

Answer 1

qualitative monitoring = Tyndall beam / smoke stick / workplace monitoring

Quantative monitoring

• capture velocity - pitot static tubes & thermal anemometer
• filter efficiency - differential pressure levels
• flow meters = measure the volume air passing through the fan
• fan direction and speed
• exhaust emission levels
• static pressures and power consumption

Question 2

Factors to be taken into account when selecting RPE

Answer 2

Nature of contamination & characteristics / duration / tasks performed - mobility & space constraints / compatibility with other PPE / individual / standards - durability & manufacturing / temperature & humidity / fit testing / training / duration / work rate / vision / explosive atmospheres

Question 3

What would you look for in a decent LEV examination report

Answer 3

LEV plant / process & substance / date of last test / performance specification / improvement actions / date / name / credentials / calibrations / legible / time period

Question 4

Outline why gloves may not offer the full level of protection

Answer 4

Selection = degree of body protection / type of material / comfort / fit / grip / dexterity / allergy

Use = procedures / training / cleaning disposal / storage / procedures

Maintenance = inspection / skin checks / supplies / repair / replacement

Question 5

Outline the range of practical measures that can encourage the use of PPE and maintain its effectiveness

Answer 5

Explain the risks / explain how the PPE will offer protection / train in the correct use (putting on & fitting - remove without contaminating - defects & damage - how to store the PPE - how to replace the PPE) / lead by example / provide storage / replacement records / employees sign for PPE / discipline for non use / reward scheme for the correct use / compatibility / views & complaints from users / face fit & testing / different sizes / facilities to clean equipment

Question 6

outline the possible reasons why RPE may not provide the level of protection stated

Answer 6

• was the right RPE selected to start with (work rate, duration, contamination exposed)
• was it manufactured to the correct standards
• is it being worn correctly (face fit test)
• are the filters working & are they correct for the contaminates
• is the power to the face mask sufficient
• does it fit correctly poor
• is it incompatible with other PPE
• is it damaged (maintainace & storage)
• are operatives trained and supervised

Question 7

what is capture velocity

Answer 7

the velocity required at a contaminant source to overcome the movement of the contaminant cloud and draw it into the hood of the LEV

Question 8

what is face velocity when measuring LEV effectiveness

Answer 8

is the average velocity of air at the open face of the hood or booth - it is measured using an anemometer

Question 9

what are the different types of anemometers

Answer 9

• rotating head anemometer - like a small windmill enclosed in a annular shroud
• heated head anemometer - relies on the airflow to cool the sensitive head which consists of a hot wire, thermocouple. a cowl is used to direct the air flow over the head - can be introduced into ducting through a sample port
• swinging vane anemometer - vane is swung inside the air chamber where the movement creates very little friction the flow through is created by the velocity at the point being measured - a probe can be inserted into a duct to measure transport velocity and provides a readout of actual velocity

Question 10

what is transport velocity and how is it measured

Answer 10

is the air velocity required to move particles and prevent a disposition in the ducts.

measured by thermal anemometers or pitot tubes

Question 11

what is a pitot tubes

Answer 11

a small device which can be measures the velocity pressure inside the ventilation system (transport velocity).

consists of two concentric tubes one facing and one at right angles - both connected to a manometer measure the pressure difference between the static pressure in the duct and the air flow

Question 12

There are two types of RPE respirators and breathing apparatus outline the equipment which Falls under each category

Answer 12

1. Respirators
   - half mask
   - full face
   - powered
2. Breathing apparatus
   - fresh air hose
   - compressed airline - constant or demand flow
   - self contained - escape / general / re circulating or re breathers

Question 13

Outline the parts of a LEV using HDFFE

Answer 13

Hood - collects the airborne contaminants at or near the source

Ducting - carries the airborne contaminants away from the work area

Filter - filters and cleans the extracted air

Fan - powers the extraction system

Exhaust - for the safe release of the cleaned extracted air

Question 14

Outline the general design features of the hood in a LEV

Answer 14

• shape & size to enclose the source
• capture & face velocity - minimise eddies
• material of construction

Question 15

Outline the general design features of the ducting in a LEV

Answer 15

• straight as possible with gentle bends
• transport velocity
• access points for regular cleaning & maintenance
• smooth internal finish

Question 16

Outline the general design features for the exhaust in a LEV

Answer 16

• exhausted air must not re enter building
• must leave at enough speed to ensure it is dispersed correctly
• positioning of exhaust using stacking
• noise created