Interview Questions & Answers - Compressed Air & Gases

1. Q. When working with pressurised cylinders,what conditions of associated storage have to be met?

 A. The cylinders must be upright and secured to prevent a fall. 

2. Q. The two hoses on an oxygen-acetylene welding/cutting set are coloured differently. Give the two colours and which is which? 

A. Blue:- Oxygen. Red:- Acetylene. 

3. Q. Is oxygen detectable by smell? 

A. No - It is an odourless gas. 

4. Q. Is oxygen lighter or heavier than air? A. Slightly Heavier. 

5. Q. Is nitrogen lighter or heavier than air? A. Slightly Lighter. 

6. Q. Is oxygen an inflammable gas? 

A. No - But it vigorously supports combustion. 

7. Q. What is the main constituent of Natural Gas? 

A. Methane. 

8. Q. What do the letters L.P.G.marked on a cylinder stand for? 

A. Liquefied Petroleum Gas. 

9. Q. What are the two main constituents of L.P.G.e.g.Calor Gas,Flogas, Bluegas etc.? 

A. Propane and Butane. 

10. Q. Is L.P.G.heavier or lighter than air? 

A. Heavier than air. 

11. Q. Is petrol vapour heavier or lighter than air? 

A. Heavier than air.

12. Q. Is chlorine gas heavier or lighter than air? 

A. Heavier than air. 

13. Q. Is acetylene gas heavier or lighter than air? 

A. Lighter than air. 

14. Q. Exposure to what toxic gas is the principal hazard in the motor repair industry? 

A. Exposure to carbon monoxide from exhaust gases. 

15. Q. Name one correct way to test for a gas leak? 

A. 1. By brushing with soapy water over suspected point of leak. 

2. Use an appropriate sensitive gas detector.

 16. Q. Is it acceptable to store all gas cylinders in the one store? 

A. No - Cylinders containing flammable or explosive gases should never be stored in the same store as oxygen. 

17. Q. The normal pressure for compressed air lines in factories is in the region of 80/100 psi.Give two dangers of using a line of this pressure for cleaning clothing and machinery? 

A. 1. The air at this pressure may be forced through the skin, and if it enters the blood stream the result could be fatal. 

2. The air at this pressure will blow around small objects that can cause accidents. 

18. Q. What is important about the pressure of compressed air supplied to a pressure vessel? 

A. It should not exceed the S.W.P. of the vessel. 

19. Q. What two things compressed air should not be used for? 

A. 1. Cleaning clothes. 2. Horse play. 

20. Q. Is it a good idea to use compressed air for the removal of swarf or dust from a machine,qualify your answer? 

A. No,particles are blown about to the danger of others.

21. Q. How is the air pressure of a system reduced? 

A. By a reducing valve. 

22. Q. Name 4 essential safety requirements which should be associated with an air receiver? 

A. 1. The Safe Working Pressure must be clearly marked on it. 
2. A suitable safety valve must be fitted. 
3. An accurate pressure gauge must be fitted. 
4. There should be an inspection manhole. 5. There should be an identification mark or number on it. 
6. There should be a drain appliance fitted.

23. Q. What is the correct procedure for joining a gas hose to a cylinder regulator? A. The hose should be connected to an approved hose connector, and all hose/connector joints should be completed by the fitting of hose clips of the jubilee or other approved type to ensure a gas tight joint. 

24. Q. What four essential precautions are necessary when handling or storing oxygen cylinders? 

A. 1. Store upright. 
2. Keep oil away from valve. 
3. Do not expose to heat. 
4. Do not drop. 

25. Q. Which of the following three gases is lighter than air? 1. Ethane? 2. Acetylene? 3. Propane? 

A. (2) Acetylene. 

26. Q. Which of the following flammable gases is lighter than air? 1. Methane? 2. Butane? 

A. (1) Methane. 

27. Q. Name four common non-flammable gases? 

A. Nitrogen, Oxygen,Argon, Nitrous Oxide, Carbon Dioxide, B.C.F., Helium

28. Q. How is (a) Carbon Monoxide formed and (b) what is it? 

A. (a) Carbon monoxide is created by the incomplete combustion of any carbon-based fuel, 
(b) It is a toxic, colorless, odorless, tasteless and nonirritant gas that is slightly less dense than air and is very soluble in water.

29. Q. What four safety precautions should be taken to control carbon monoxide exposure in a workplace? 

A. 1. Keep rooms properly ventilated when gas appliances are operating. 
2. Keep gas appliances properly maintained and serviced at regular intervals. 
3. Portable petrol/diesel engines should never be run indoors in a confined space. 
4. Where forklift trucks or similar are used indoors in warehouses, etc. advice should be sought from the regulatory authorities or suppliers. 

30. Q. What two sectors or occupations are most likely to be affected by fatal carbon monoxide poisoning? 

A. The occupations most affected in terms of fatal accidents are:

• Security workers and night watchman 

• Those working in poorly ventilated atmosphere where gas is used for heating.

31. Q. What are the similar and dissimilar distinguishing features between threads of combustible and non-combustible gas cylinders? 

A. 1. The cylinders have the same screwed thread size. 
2. Right-hand threads are on oxygen and noncombustible gas cylinders. 
3. Left-hand threads are on acetylene and other combustible gas cylinders. 

32. Q. What gas would you expect to find in each of the three cylinders colour coded by BOC as follows:(a)Black, (b)Maroon/Chocolate, (c) Red with white dot? 

A. (a) Oxygen. (b) Acetylene. (c) Hydrogen.