IICRC HST Exam Questions and
Answers with rationale Top Rated
2026
1. What is Industrial Hygiene (or Occupational Health and Safety)?
Answer: The science and art devoted to the anticipation, recognition,
evaluation, prevention, and control of those environmental factors or
stresses arising in or from the workplace which may cause sickness,
impaired health and well-being, or significant discomfort among
workers or among citizens of the community. Rationale: This definition
underpins the entire HST certification. It shifts focus from mere
compliance to proactive prevention of workplace hazards in restoration
work (e.g., mold, chemicals, water damage environments).
2. What are the three basic criteria for health and safety hazard
identification? Answer: Recognition of a hazard or potential hazard;
Assessment and evaluation of the hazard; Controls that are implemented
to minimize the hazard. Rationale: Hazard identification follows a
logical process: spot the issue, measure its severity, then apply fixes.
This is foundational before any job site work in restoration.
3. Define Hazard vs. Risk. Answer:
• Hazard: Any source or situation with a potential for harm (injury,
ill health, property damage, or environmental damage).
• Risk: The chance or probability that a person will be harmed or
experience an adverse health effect if exposed to the hazard (can
also include property/equipment loss). Rationale: Hazards exist
independently; risk depends on exposure and likelihood. In
restoration (e.g., Category 3 water or mold), distinguishing them
drives proper controls.
4. What is the purpose of a hazard/risk assessment? Answer: To
identify hazards and risks in the workplace so that workers are made
,aware of unsafe conditions at a worksite. Rationale: Assessments aim to
remove hazards or reduce risk through precautions/controls. Levels of
risk range from Very Low (acceptable) to Very High, guiding decision-
making on whether additional measures are needed (considering cost for
medium risks).
5. What is the primary goal of the Global Harmonized System
(GHS)? Answer: To promote common criteria for classifying chemicals
according to their health, physical, and environmental hazards
(standardizing classification and labeling worldwide). Rationale: GHS
creates a universal system for hazard communication, reducing
confusion across borders and improving worker protection in industries
using cleaning/restoration chemicals. It does not replace other
regulations but complements them.
6. In GHS, what does the signal word on a label indicate? Answer:
The level of severity of the hazard ("Danger" for more severe;
"Warning" for less severe). Rationale: Signal words help workers
quickly gauge risk. Pictograms provide a universal visual language (e.g.,
corrosion pictogram requires avoiding skin/eye contact and using PPE).
7. What should be prioritized in an emergency response plan?
Answer: Ensuring everyone's safety. Rationale: Safety comes first in
any plan—before costs, speed, or comfort. This includes evacuation,
first aid, and communication. In restoration, this applies to scenarios like
chemical spills, fire, or structural collapse.
8. When should workers receive training on GHS/hazard
communication? Answer: As part of their initial onboarding process
(and often annually or when new hazards are introduced). Rationale:
Training ensures workers know where to find hazard info, what the
hazards are, how they are protected, and what to do in emergencies. At
the end of HAZCOM training, workers should be able to answer those
four key questions.
,9. What is the purpose of Safety Data Sheets (SDS)? Answer: To
provide detailed information on the safe handling, use, hazards, and
protective measures for chemicals (all of the above in many multiple-
choice formats). Rationale: SDS replaced older MSDS under GHS.
They support compliance, worker awareness, and proper response to
exposures in restoration jobs involving cleaners, disinfectants, or
antimicrobials.
10. Which of the following is a key principle of health and safety in
restoration industries? Answer: All of the above — risk assessment,
hazard communication (GHS), and proper use of PPE. Rationale: HST
stresses the hierarchy of controls (elimination > substitution >
engineering > administrative > PPE). PPE (goggles, gloves, respirators)
is the last line of defense when handling chemicals or biohazards.
Hierarchy of Controls & Hazard Controls
11. What is the correct order of the Hierarchy of Hazard Controls
(from most to least effective)? Answer: Elimination/Substitution →
Engineering Controls → Administrative Controls/Work Practices →
PPE. Rationale: The hierarchy prioritizes removing the hazard entirely
(most effective) before relying on worker behavior or equipment. In
restoration, eliminate a chemical hazard by substituting a safer product;
use ventilation (engineering) before training or gloves (PPE is the last
line of defense). If risk cannot be reduced adequately, the work should
be prohibited.
12. Which control is an example of an Engineering Control?
Answer: Installing local exhaust ventilation or modifying equipment to
reduce exposure. Rationale: Engineering controls physically isolate or
remove the hazard at the source (e.g., HEPA air scrubbers on a mold job
or guards on machinery). They are more reliable than administrative
controls or PPE because they don’t depend on human compliance.
13. When is PPE considered the appropriate primary control?
Answer: When higher-level controls (elimination, substitution,
, engineering, administrative) are not feasible or sufficient to reduce risk
to an acceptable level. Rationale: PPE (gloves, respirators, goggles,
suits) protects the individual but does not remove the hazard. HST
emphasizes using it as a supplement, not a substitute, for better
controls—common in Category 3 water or chemical applications.
Respiratory Protection
14. What does PEL stand for, and what does it indicate? Answer:
Permissible Exposure Limit — the maximum time-weighted average
concentration of an airborne contaminant to which a worker may be
exposed without respiratory protection. Rationale: PELs (set by OSHA)
help determine when respirators or other controls are required. In
restoration, this applies to mold spores, silica dust, or chemical vapors;
monitoring may be needed on large jobs.
15. What are the three employer requirements for workers who
need respirators? Answer: Medical evaluation, fit testing, and training.
Rationale: Respirators must be NIOSH-approved. Training covers
proper use, limitations, maintenance, and cleaning. Fit testing ensures a
proper seal. This is critical for half-face or full-face respirators used in
contaminated environments.
16. In the hierarchy applied to respiratory hazards, what comes
before PPE (respirators)? Answer: Elimination/substitution,
engineering controls (e.g., ventilation), and administrative/work practice
controls. Rationale: Always try to control the source or exposure level
first. For example, use negative air pressure and HEPA filtration before
relying solely on respirators.
Bloodborne Pathogens (BBP) & Biohazards
17. What does the OSHA Bloodborne Pathogens Standard primarily
address? Answer: Safeguards to protect workers from health hazards
caused by bloodborne pathogens (e.g., HIV, Hepatitis B, Hepatitis C)
through exposure control plans, universal precautions, engineering/work
Answers with rationale Top Rated
2026
1. What is Industrial Hygiene (or Occupational Health and Safety)?
Answer: The science and art devoted to the anticipation, recognition,
evaluation, prevention, and control of those environmental factors or
stresses arising in or from the workplace which may cause sickness,
impaired health and well-being, or significant discomfort among
workers or among citizens of the community. Rationale: This definition
underpins the entire HST certification. It shifts focus from mere
compliance to proactive prevention of workplace hazards in restoration
work (e.g., mold, chemicals, water damage environments).
2. What are the three basic criteria for health and safety hazard
identification? Answer: Recognition of a hazard or potential hazard;
Assessment and evaluation of the hazard; Controls that are implemented
to minimize the hazard. Rationale: Hazard identification follows a
logical process: spot the issue, measure its severity, then apply fixes.
This is foundational before any job site work in restoration.
3. Define Hazard vs. Risk. Answer:
• Hazard: Any source or situation with a potential for harm (injury,
ill health, property damage, or environmental damage).
• Risk: The chance or probability that a person will be harmed or
experience an adverse health effect if exposed to the hazard (can
also include property/equipment loss). Rationale: Hazards exist
independently; risk depends on exposure and likelihood. In
restoration (e.g., Category 3 water or mold), distinguishing them
drives proper controls.
4. What is the purpose of a hazard/risk assessment? Answer: To
identify hazards and risks in the workplace so that workers are made
,aware of unsafe conditions at a worksite. Rationale: Assessments aim to
remove hazards or reduce risk through precautions/controls. Levels of
risk range from Very Low (acceptable) to Very High, guiding decision-
making on whether additional measures are needed (considering cost for
medium risks).
5. What is the primary goal of the Global Harmonized System
(GHS)? Answer: To promote common criteria for classifying chemicals
according to their health, physical, and environmental hazards
(standardizing classification and labeling worldwide). Rationale: GHS
creates a universal system for hazard communication, reducing
confusion across borders and improving worker protection in industries
using cleaning/restoration chemicals. It does not replace other
regulations but complements them.
6. In GHS, what does the signal word on a label indicate? Answer:
The level of severity of the hazard ("Danger" for more severe;
"Warning" for less severe). Rationale: Signal words help workers
quickly gauge risk. Pictograms provide a universal visual language (e.g.,
corrosion pictogram requires avoiding skin/eye contact and using PPE).
7. What should be prioritized in an emergency response plan?
Answer: Ensuring everyone's safety. Rationale: Safety comes first in
any plan—before costs, speed, or comfort. This includes evacuation,
first aid, and communication. In restoration, this applies to scenarios like
chemical spills, fire, or structural collapse.
8. When should workers receive training on GHS/hazard
communication? Answer: As part of their initial onboarding process
(and often annually or when new hazards are introduced). Rationale:
Training ensures workers know where to find hazard info, what the
hazards are, how they are protected, and what to do in emergencies. At
the end of HAZCOM training, workers should be able to answer those
four key questions.
,9. What is the purpose of Safety Data Sheets (SDS)? Answer: To
provide detailed information on the safe handling, use, hazards, and
protective measures for chemicals (all of the above in many multiple-
choice formats). Rationale: SDS replaced older MSDS under GHS.
They support compliance, worker awareness, and proper response to
exposures in restoration jobs involving cleaners, disinfectants, or
antimicrobials.
10. Which of the following is a key principle of health and safety in
restoration industries? Answer: All of the above — risk assessment,
hazard communication (GHS), and proper use of PPE. Rationale: HST
stresses the hierarchy of controls (elimination > substitution >
engineering > administrative > PPE). PPE (goggles, gloves, respirators)
is the last line of defense when handling chemicals or biohazards.
Hierarchy of Controls & Hazard Controls
11. What is the correct order of the Hierarchy of Hazard Controls
(from most to least effective)? Answer: Elimination/Substitution →
Engineering Controls → Administrative Controls/Work Practices →
PPE. Rationale: The hierarchy prioritizes removing the hazard entirely
(most effective) before relying on worker behavior or equipment. In
restoration, eliminate a chemical hazard by substituting a safer product;
use ventilation (engineering) before training or gloves (PPE is the last
line of defense). If risk cannot be reduced adequately, the work should
be prohibited.
12. Which control is an example of an Engineering Control?
Answer: Installing local exhaust ventilation or modifying equipment to
reduce exposure. Rationale: Engineering controls physically isolate or
remove the hazard at the source (e.g., HEPA air scrubbers on a mold job
or guards on machinery). They are more reliable than administrative
controls or PPE because they don’t depend on human compliance.
13. When is PPE considered the appropriate primary control?
Answer: When higher-level controls (elimination, substitution,
, engineering, administrative) are not feasible or sufficient to reduce risk
to an acceptable level. Rationale: PPE (gloves, respirators, goggles,
suits) protects the individual but does not remove the hazard. HST
emphasizes using it as a supplement, not a substitute, for better
controls—common in Category 3 water or chemical applications.
Respiratory Protection
14. What does PEL stand for, and what does it indicate? Answer:
Permissible Exposure Limit — the maximum time-weighted average
concentration of an airborne contaminant to which a worker may be
exposed without respiratory protection. Rationale: PELs (set by OSHA)
help determine when respirators or other controls are required. In
restoration, this applies to mold spores, silica dust, or chemical vapors;
monitoring may be needed on large jobs.
15. What are the three employer requirements for workers who
need respirators? Answer: Medical evaluation, fit testing, and training.
Rationale: Respirators must be NIOSH-approved. Training covers
proper use, limitations, maintenance, and cleaning. Fit testing ensures a
proper seal. This is critical for half-face or full-face respirators used in
contaminated environments.
16. In the hierarchy applied to respiratory hazards, what comes
before PPE (respirators)? Answer: Elimination/substitution,
engineering controls (e.g., ventilation), and administrative/work practice
controls. Rationale: Always try to control the source or exposure level
first. For example, use negative air pressure and HEPA filtration before
relying solely on respirators.
Bloodborne Pathogens (BBP) & Biohazards
17. What does the OSHA Bloodborne Pathogens Standard primarily
address? Answer: Safeguards to protect workers from health hazards
caused by bloodborne pathogens (e.g., HIV, Hepatitis B, Hepatitis C)
through exposure control plans, universal precautions, engineering/work
