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100+ Free HKIE Professional Assessment — Gas Discipline Practice Questions
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2026 Statistics
Key Facts: HKIE Professional Assessment — Gas Discipline Exam
Portfolio+Essay
Assessment Format
HKIE PA Regulations
2 Hours
Written Essay Duration
HKIE PA Regulations
HK$ 3,100
Total Assessment Fee
HKIE Fee Schedule 2026
4 Areas
HKIE Competence Standard
HKIE Competence Standards
45 Mins
Interview Duration
HKIE Interview Standards
MHKIE
Target Qualification
HKIE Membership Regulations
This exam prep resource provides 100 multiple-choice questions designed as an English-language study adaptation for gas engineering principles, HK Gas Safety Ordinance (Cap. 51), Gas Authority (EMSD) Code of Practice, Town Gas distribution, LPG bulk storage & cylinder installations, gas utilization equipment, safety devices, and HKIE ethics. It serves as a technical knowledge self-assessment tool and does not replace the official HKIE competence portfolio review, interview, or technical essay.
Sample HKIE Professional Assessment — Gas Discipline Practice Questions
Try these sample questions to test your HKIE Professional Assessment — Gas Discipline exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.
1What is the Wobbe Index (W) of a fuel gas having a gross calorific value (H_v) of 17.2 MJ/m³ and a specific gravity (SG) of 0.55 relative to air?
A.23.19 MJ/m³
B.31.27 MJ/m³
C.9.46 MJ/m³
D.12.76 MJ/m³
Explanation: The Wobbe Index is calculated using the formula W = H_v / sqrt(SG). Substituting the given values: W = 17.2 / sqrt(0.55) = 17.2 / 0.7416 = 23.19 MJ/m³. The Wobbe Index is a critical indicator of fuel gas interchangeability for gas burners.
2Which chemical component constitutes the largest volumetric percentage in Hong Kong Town Gas manufactured by naphtha steam reforming?
A.Hydrogen (H2), approximately 49%
B.Methane (CH4), approximately 75%
C.Carbon monoxide (CO), approximately 30%
D.Propane (C3H8), approximately 50%
Explanation: Hong Kong Town Gas produced via naphtha steam reforming comprises approximately 49% Hydrogen (H2), 28.5% Methane (CH4), 16.5% Carbon Dioxide (CO2), and about 3% Carbon Monoxide (CO) and Nitrogen (N2). Hydrogen's high concentration gives Town Gas a lower specific gravity (~0.52) and high flame speed.
3Why is commercial LPG (Liquefied Petroleum Gas) considered particularly hazardous when leaked in enclosed or low-lying areas in Hong Kong?
A.LPG has a specific gravity greater than 1.0, causing it to sink and accumulate in drains, basements, and floor levels.
B.LPG is lighter than air and rapidly collects at high ceiling voids creating unvented pockets.
C.LPG spontaneously ignites at ambient Hong Kong temperatures above 25°C without a source of ignition.
D.LPG decomposes into toxic chlorine gas upon exposure to ambient humidity.
Explanation: Commercial LPG (propane/butane mixtures) has a relative density of 1.5 to 2.0 times that of air. Because it is heavier than air, leaked LPG sinks to ground level, basements, trenches, and drains, creating explosive vapor pockets rather than dissipating upwards like Town Gas.
4What are the approximate Lower Flammable Limit (LFL) and Upper Flammable Limit (UFL) of Methane (CH4) in air by volume at standard conditions?
A.LFL = 5%, UFL = 15%
B.LFL = 2.1%, UFL = 9.5%
C.LFL = 1.8%, UFL = 8.4%
D.LFL = 12.5%, UFL = 74%
Explanation: Methane has a Lower Flammable Limit (LFL) of approximately 5.0% and an Upper Flammable Limit (UFL) of 15.0% by volume in air. Within this concentration window, a methane-air mixture will ignite and sustain combustion if an ignition source is introduced.
5A gas water heater consumes Town Gas (gross CV = 17.2 MJ/m³) at a rate of 3.6 m³/h. What is the gross heat input rating of the appliance in kW?
A.17.2 kW
B.61.9 kW
C.4.78 kW
D.22.5 kW
Explanation: Heat input Q (kW) = [Flow rate (m³/h) × Gross CV (MJ/m³)] / 3.6. Substituting the values: Q = (3.6 × 17.2) / 3.6 = 17.2 kW. The factor 3.6 converts MJ/h to kW (since 1 kW = 3.6 MJ/h).
6Complete combustion of 1 m³ of pure Propane (C3H8) requires how many m³ of stoichiometric dry air (assuming air contains 21% O2 by volume)?
A.23.8 m³
B.5.0 m³
C.11.9 m³
D.2.0 m³
Explanation: The chemical equation for complete propane combustion is C3H8 + 5 O2 -> 3 CO2 + 4 H2O. Thus, 1 m³ of propane requires 5 m³ of pure oxygen. Volume of dry air required = 5 / 0.21 = 23.81 m³.
7A gas mixture contains 80% Methane (LFL = 5.0%) and 20% Propane (LFL = 2.1%) by volume. Using Le Chatelier's equation, what is the Lower Flammable Limit (LFL) of the gas mixture?
A.3.92%
B.4.42%
C.3.55%
D.2.80%
Explanation: Le Chatelier's equation states LFL_mix = 100 / sum(y_i / LFL_i). Here sum = (80 / 5.0) + (20 / 2.1) = 16.0 + 9.524 = 25.524. LFL_mix = 100 / 25.524 = 3.918% (approx 3.92%).
8Under Hong Kong gas safety standards, what is the statutory purpose of odorizing Town Gas and LPG with chemical odorants like ethyl mercaptan or THT?
A.To ensure that gas leaks become readily detectable by smell at a concentration of no more than 20% of the gas Lower Flammable Limit (LFL).
B.To increase the gross calorific value and flame stability of manufactured town gas.
C.To act as a corrosion inhibitor for interior copper and polyethylene gas pipework.
D.To reduce the emission of carbon monoxide during partial combustion.
Explanation: Hong Kong Gas Safety Regulations mandate that fuel gases distributed to consumers must be distinctively odorized (using ethyl mercaptan or tetrahydrothiophene) so that any gas leakage into air can be detected by normal human olfaction at or below 1/5th (20%) of the gas's Lower Flammable Limit.
9In a gas appliance combustion chamber, what primary operational factor causes the ratio of Carbon Monoxide to Carbon Dioxide (CO/CO2 ratio) to exceed the safe limit of 0.02?
A.Insufficiency of primary or secondary combustion air leading to incomplete combustion and flame chilling.
B.Excessive aeration causing flame lift-off and complete oxidation to H2O and CO2.
C.High gas supply pressure resulting in complete stoichiometric reaction.
D.Using pure propane instead of butane in a multi-gas burner.
Explanation: A CO/CO2 ratio exceeding 0.02 indicates incomplete combustion caused by insufficient primary or secondary air supply, combustion chamber flame impingement on cold surfaces (chilling), or flue gas recirculation. Excessive CO is extremely toxic and lethal.
10Town Gas in Hong Kong belongs to First Family Gas (manufactured gas). If a burner designed for First Family gas is supplied with Second Family gas (Natural Gas, W ≈ 50 MJ/m³) without modification, what will occur?
A.Severe thermal over-firing, incomplete combustion, heavy CO production, and potential burner overheating due to double the Wobbe Index.
B.Burner flame extinction due to insufficient gas velocity through the injector orifice.
C.Immediate flashback of the flame into the burner mixing tube.
D.Reduction of heat output by 50% due to higher gas density.
Explanation: First Family gases (Town Gas) have a lower Wobbe Index (~23 MJ/m³) than Second Family gases (~50 MJ/m³). Supplying a higher Wobbe Index gas through an unmodified First Family injector orifice results in roughly double the heat energy input, overwhelming available aeration, producing severe CO emissions, and risking structural burner failure.
About the HKIE Professional Assessment — Gas Discipline Practice Questions
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