REHS Exam Content Breakdown: The 17 Modules You Need to Master

A detailed overview of each REHS exam module, including what's covered, relative difficulty, and what to expect on exam day.

The California REHS exam spans 17 distinct modules covering everything from food safety to toxicology to vector control. Knowing what each module contains—and how deeply you need to know it—is essential for efficient studying. Not all modules are weighted equally, and not all candidates struggle with the same content.

Here's what you're actually studying for.

Foundation modules: Start here

Module 1: General Environmental Health, Statutes & Administration

California Health & Safety Code, Title 22 regulations, CDPH role, local health officer duties, record-keeping, and legal authority. This module sets the regulatory framework for everything else. Master it thoroughly. You'll reference it constantly.

Module 17: Epidemiology Concepts & Calculations

Attack rate, secondary attack rate, incidence, prevalence, outbreak investigation procedures. Includes calculations. Straightforward module but easy to miss nuances in how rates are calculated or interpreted.

Food and water safety: Highest-weighted content

Module 2: Food Protection & CalCode

The California Retail Food Code. Temperature controls, cross-contamination, food handling, inspection procedures, violations and corrective actions. This module appears heavily on the exam. Expect scenario questions about specific food safety violations.

Module 3: Communicable & Foodborne Disease

Pathogenic organisms, foodborne illness outbreaks, disease transmission routes, investigation procedures. Ties directly to Module 2. If you understand the causative agents, you understand the CalCode rules that prevent them.

Module 4: Dairy & Milk Science

Pasteurization, raw milk regulations, dairy processing standards, testing requirements. Specialized content but not heavily tested. Study thoroughly but don't spend disproportionate time here.

Module 5: Potable Water (Drinking Water)

Water quality standards, contaminants, testing protocols, treatment methods, distribution system safety. Core content. Expect questions on specific contaminant limits and violation procedures.

Module 6: Liquid Waste & Wastewater

Treatment standards, discharge limits, septic systems, greywater regulations. Moderately complex. Understand the regulatory limits and treatment hierarchy.

Environmental management: Moderate weight

Module 7: Solid Waste Management

Landfill operations, composting, recycling standards, hazardous waste separation. Straightforward module. Questions focus on regulatory classifications and handling procedures.

Module 8: Hazardous Materials & Underground Storage Tanks

Tank installation and maintenance, spill response, permitting, hazardous waste definitions. Technical but systematic. Understanding the regulatory triggers and response procedures is key.

Module 9: Medical Waste

Classification, segregation, storage, treatment, and disposal. Short module covering specific regulatory requirements. Memorize the categories and handling rules.

Module 10: Recreational Health (Pools & Spas)

Water chemistry, filtration, circulation rates, disinfection, design standards. Math-heavy (turnover calculations, chlorine residuals). Know the formulas and standards cold.

Specialized environmental health

Module 11: Housing & Institutions

Habitability standards, ventilation, sanitation, pest control, institutional facilities. Mix of regulations and practical application. Understand minimum standards for different facility types.

Module 12: Vector Control & Pest Management

Arthropod identification, pest management strategies, pesticide regulations. Entomology can feel unfamiliar. Focus on disease vectors and control methods. Don't overthink insect taxonomy.

Module 13: Air Pollution & Toxicology

Toxicology principles, dose-response, air quality standards, indoor air. "The dose makes the poison." Understand exposure pathways and threshold limits. Questions span air quality regulations and basic toxicology.

Module 14: Light, Noise, Radiation & Sampling

Decibel levels, radiation exposure limits, sampling procedures, environmental monitoring. Miscellaneous module. Memorize specific threshold values and sampling standards.

Module 15: Disaster Response & Personal Protective Equipment

PPE selection, decontamination, emergency response protocols. Practical module. Know PPE ratings and when each type is required.

Module 16: Body Art Facilities (AB 300)

Tattoo and piercing regulations specific to California. Short, niche content. Master the specific infection control and facility standards.

Which modules demand the most study time?

Not all modules are created equal. Modules 2, 3, 5, and 6 (food and water) consume significant exam weight and regulatory complexity. Module 10 (pools) requires calculation fluency. Modules 12 and 13 challenge candidates unfamiliar with vector control and toxicology.

Prioritize modules where regulatory detail is dense and scenario questions are likely. That's where passing candidates separate from those who don't.

How to approach learning each module

For each module: Learn the core regulatory framework first. Then work through knowledge checks and scenario questions. Use memory aids for dense regulatory detail. Finally, take mixed practice questions that combine this module with others to mirror exam conditions.

The bottom line

The REHS exam tests regulatory knowledge and practical judgment across 17 distinct domains. Know what each module contains, understand which are weighted most heavily, and allocate study time accordingly. Some modules reward deep mastery; others reward accurate memorization. Both approaches matter.