DentalingoExam guide
Radiation Health and Safety exam: format, domains and how to study
The DANB® RHS® exam is one of the three components of the CDA® certification exam and one of the three of the NELDA® exam. It has 75 multiple-choice questions and a 60-minute time limit.
Format
| Questions | 75 multiple-choice |
|---|---|
| Time | 60 minutes |
| Delivery | Computer-adaptive testing (CAT), at a test center or with remote online proctoring |
| Outline in effect | Since March 12, 2025 |
Content domains and weights
Each candidate gets the same share of questions from each domain. At 75 questions, that is roughly:
| Domain | Weight | About |
|---|---|---|
| Purpose and Technique | 50 % | 37 questions |
| Radiation Characteristics and Protection | 25 % | 19 questions |
| Infection Prevention and Control | 25 % | 19 questions |
Source: the RHS® exam outline and the exam page on danb.org. Exam facts read from danb.org on October 15, 2026.
How to study for it
- Study in proportion to the weights. The DANB® exam-preparation page advises starting from the exam outline and its percentages; here Purpose and Technique alone is 50 % of the exam.
- Keep one textbook from the outline’s reference list. The RHS® exam outline lists the textbooks and reference materials used to develop the exam, and the same page suggests having at least one recommended dental assisting textbook.
- Practise against the clock. 75 questions in 60 minutes leaves about 48 seconds a question.
- Give it time. According to the same page, many test-takers say they studied for at least one to two months, and it suggests setting aside a few hours each week; it also offers a demo exam to show the screens beforehand.
Source: Prepare for Exams, danb.org.
Practice questions
A free practice test across the exam’s domains, drawn from Dentalingo’s 400 questions for it. Each answer is explained the moment you choose, with the public source it was checked against.
Start the Radiation Health and Safety practice testPractice test 2
Free reference
Radiolucent vs radiopaqueWhat looks dark and what looks light on a dental radiograph, and the three angulation errors.Read radiolucent vs radiopaqueTooth numbering chartAll 52 permanent and primary teeth in the Universal, Palmer and FDI systems, with a converter and a source for every rule.Open the tooth numbering chartThe app
Practise for the Radiation Health and Safety exam in Dentalingo
400 practice questions for the DANB® RHS® exam, in short lessons across its three domains, each answer explained and checked against a cited source.
A timed mock exam of 75 questions in 60 minutes, spaced review of what you miss, and readiness for each domain.
The first 7 questions are free. After that, full access is a Study Camp subscription; the App Store shows the price in your country. More about the app
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Spaced review of what you missed
Answers explained the moment you choose
XP and accuracy over time