FE Other Disciplines (NCEES Fundamentals of Engineering) — All Questions

After three half-lives have elapsed, what fraction of a radioactive substance remains?

• a.50%
• b.12.5%✓
• c.25%
• d.33%

Each half-life halves the remaining amount: (1/2)^3 = 1/8 = 0.125 = 12.5%. The general relation is N/N0 = (1/2)^(t/T_half), central to radiation-exposure and toxicology calculations.

An atmosphere is generally classified as oxygen-deficient (a confined-space hazard) when the oxygen concentration falls below what value?

• a.16%
• b.20.9%
• c.19.5%✓
• d.23.5%

Normal air is about 20.9% oxygen. OSHA classifies an atmosphere as oxygen-deficient below 19.5% and oxygen-enriched above 23.5%. Confined-space entry requires atmospheric testing before entry.

Under OSHA, the permissible noise exposure limit for an 8-hour workday is:

• a.120 dBA
• b.70 dBA
• c.140 dBA
• d.90 dBA✓

OSHA's 8-hour PEL for noise is 90 dBA, with a 5-dBA exchange rate that halves allowable time for each increase. A hearing-conservation program begins at the 85-dBA action level.

A vapor's concentration is below its lower explosive limit (LEL). The mixture is:

• a.In the ideal ignition range
• b.Too rich to ignite
• c.Too lean (too little fuel) to ignite✓
• d.Oxygen-enriched

Below the LEL there is too little fuel vapor for combustion (too lean); above the UEL it is too rich. Only between the LEL and UEL will the mixture ignite.

The fire tetrahedron adds which fourth element to the classic fire triangle of fuel, heat, and oxygen?

• a.Smoke
• b.A sustained chemical chain reaction✓
• c.Pressure
• d.Water

The tetrahedron adds the self-sustaining chemical chain reaction. Removing any one of the four elements (as dry-chemical agents do to the reaction) extinguishes the fire.

A Class B fire extinguisher is designed primarily for fires involving:

• a.Flammable liquids and gases✓
• b.Ordinary combustibles like wood and paper
• c.Energized electrical equipment
• d.Combustible metals

Class B covers flammable liquids and gases. Class A is ordinary combustibles, Class C is energized electrical equipment, and Class D is combustible metals.

The primary purpose of an OSHA lockout/tagout (LOTO) program is to:

• a.Provide fall protection at height
• b.Reduce airborne dust
• c.Control hazardous energy so machines cannot start during servicing✓
• d.Label chemical containers

LOTO isolates and de-energizes equipment and locks it out so stored or accidental energy cannot injure workers performing maintenance or servicing.

Under the OSHA Hazard Communication Standard (GHS-aligned), a Safety Data Sheet (SDS) has how many standardized sections?

• a.24
• b.8
• c.4
• d.16✓

The globally harmonized SDS format has 16 sections in a fixed order, from identification and hazards through handling, exposure controls, and disposal.

In radiation protection, the ALARA principle directs that exposures be kept:

• a.At the regulatory maximum
• b.Zero at all costs regardless of feasibility
• c.Exactly at background level
• d.As low as reasonably achievable✓

ALARA means As Low As Reasonably Achievable, balancing dose reduction against social and economic factors using time, distance, and shielding to minimize exposure.

The gray (Gy), the SI unit of absorbed radiation dose, is defined as:

• a.One roentgen per hour
• b.One radioactive disintegration event occurring each second
• c.One rem per year
• d.One joule of energy absorbed per kilogram of matter✓

1 Gy = 1 J/kg of absorbed energy. The sievert then weights the gray by radiation type to express biological dose equivalent.

In the hierarchy of hazard controls, which approach is considered most effective (highest priority)?

• a.Elimination of the hazard✓
• b.Administrative procedures
• c.Warning signs
• d.Personal protective equipment

Elimination (removing the hazard entirely) is most effective, followed by substitution, engineering controls, administrative controls, and finally PPE as the last line of defense.

Personal protective equipment (PPE) is placed where in the hierarchy of controls?

• a.It is not a control method
• b.First, as the preferred control
• c.Last, as the least effective control✓
• d.Equal to elimination

PPE is the least effective control because it protects only the wearer and only when used correctly; it is used when higher-level controls cannot fully remove the hazard.

OSHA generally requires fall protection in the construction industry at heights of:

• a.10 feet or more
• b.6 feet or more✓
• c.2 feet or more
• d.20 feet or more

In construction, fall protection is generally required at 6 feet above a lower level. General industry uses a 4-foot trigger height.

Before entering a permit-required confined space, the FIRST safety step is generally to:

• a.Remove all ventilation equipment
• b.Begin the assigned maintenance work as quickly as possible
• c.Assume the atmosphere is safe
• d.Test the atmosphere for oxygen, flammables, and toxics✓

Atmospheric testing for oxygen level, flammable gases, and toxic contaminants must precede entry, since invisible atmospheric hazards are the leading cause of confined-space fatalities.

Two identical machines each produce 80 dB of sound. Operating together as incoherent sources, their combined level is about:

• a.160 dB
• b.80 dB
• c.83 dB✓
• d.100 dB

Doubling sound power adds about 3 dB (10*log10(2) is about 3), so two equal 80-dB sources give roughly 83 dB, not 160 dB, because decibels are logarithmic.

In water-quality engineering, biochemical oxygen demand (BOD) measures:

• a.The dissolved salt content
• b.The overall acidity or alkalinity (pH) of the water sample
• c.The turbidity of the water
• d.The oxygen microbes consume to decompose organic matter✓

BOD quantifies the dissolved oxygen that microorganisms use to break down organic matter; a high BOD signals heavy organic pollution that can deplete a stream's oxygen.

Discharging a high-BOD effluent into a river primarily harms aquatic life by:

• a.Cooling the water
• b.Sharply raising the water's pH to chemically toxic levels
• c.Depleting dissolved oxygen as microbes consume it✓
• d.Increasing dissolved oxygen

Microbes decomposing the organic load consume dissolved oxygen faster than reaeration replaces it, causing an oxygen sag that can suffocate fish and other aquatic organisms.

A contaminant present at 2 mg/L in water corresponds to approximately how many ppm?

• a.2 ppm✓
• b.200 ppm
• c.20 ppm
• d.0.2 ppm

Because 1 L of water weighs about 1 kg (10^6 mg), 1 mg/L is about 1 ppm. Thus 2 mg/L is about 2 ppm. This equivalence holds for dilute aqueous solutions.

Carbon monoxide is especially dangerous in confined workspaces primarily because it:

• a.Is extremely flammable and readily forms explosive mixtures even at very low concentrations
• b.Is colorless, odorless, and binds hemoglobin far more strongly than oxygen✓
• c.Is strongly acidic
• d.Has a sharp warning odor

CO is colorless and odorless (no warning) and binds hemoglobin with roughly 200 times oxygen's affinity, forming carboxyhemoglobin and causing chemical asphyxiation.

The flash point of a liquid is the:

• a.Temperature at which the liquid spontaneously self-ignites in air with no external spark or flame
• b.Lowest temperature at which it gives off enough vapor to form an ignitable mixture✓
• c.Temperature at which it freezes
• d.Temperature at which it boils

Flash point is the minimum temperature at which a liquid produces sufficient vapor to flash when an ignition source is present. Autoignition, needing no spark, occurs at a higher temperature.

A chemical's Threshold Limit Value, Time-Weighted Average (TLV-TWA) represents the:

• a.Concentration that causes an explosion
• b.Instantaneous airborne concentration that would prove immediately lethal to an exposed worker on contact
• c.Average airborne concentration a worker may be exposed to over an 8-hour shift without adverse effect✓
• d.Odor detection threshold

TLV-TWA is the time-weighted average concentration for a normal 8-hour day and 40-hour week to which nearly all workers may be repeatedly exposed without adverse health effects.

In toxicology, the LD50 of a substance is the dose that:

• a.Just begins to cause mild irritation
• b.Causes a detectable odor
• c.Is lethal to 50% of a test population✓
• d.Is completely safe for all subjects

LD50 (median lethal dose) kills 50% of a test population; a lower LD50 means higher acute toxicity. It is a standard measure for comparing chemical hazards.

OSHA's recordable incident rate is normalized using a base of how many employee-hours, representing 100 full-time workers per year?

• a.200,000✓
• b.1,000,000
• c.100,000
• d.40,000

The rate = (recordable cases x 200,000)/total hours worked. The 200,000 base equals 100 workers x 40 hours x 50 weeks, allowing comparison across differently sized firms.

Which of the following is a form of ionizing radiation?

• a.Visible light
• b.Microwaves
• c.Gamma rays✓
• d.Radio waves

Gamma rays, along with X-rays and alpha and beta particles, carry enough energy to remove electrons from atoms (ionize) and damage tissue. Visible light, radio, and microwaves are non-ionizing.

Local exhaust ventilation is generally preferred over general dilution ventilation for a toxic contaminant because it:

• a.Increases the room contaminant concentration
• b.Requires no maintenance
• c.Captures the contaminant at its source before it spreads✓
• d.Uses no energy

Local exhaust captures contaminants at the point of generation, removing them before workers breathe them, which is more effective and lower-flow than diluting contaminated air throughout the room.

Redesigning a process so the hazard is removed entirely, rather than guarded against, reflects which principle?

• a.Engineering out the hazard (prevention through design)✓
• b.Posting more warning signs
• c.Accepting the residual risk
• d.Relying on PPE first

Prevention through design engineers the hazard out of the process itself, far more reliable than depending on worker behavior, signs, or PPE to manage a hazard left in place.