> ## Documentation Index
> Fetch the complete documentation index at: https://docs.repdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Sample Exclusions

> Prevent repeat respondents from prior projects when running tracker studies or fresh-sample waves.

Sample exclusions block respondents who participated in selected prior projects from entering a new project. This is essential for tracker studies, wave research, and any project that requires fresh respondents.

## When to use exclusions

| Scenario              | Why exclusions matter                                                             |
| --------------------- | --------------------------------------------------------------------------------- |
| **Tracker studies**   | Each wave should capture new respondents, not repeats from prior waves            |
| **Recontact studies** | Inverse case — you may want to target prior respondents instead of excluding them |
| **Category refresh**  | Avoid respondents who recently completed a similar study                          |

## Setting up exclusions

1. Open the project (or use the exclusions modal during project setup)
2. Search for prior projects to exclude
3. Save the exclusion list before launching sources

The search experience matches the project search used elsewhere in Research Desk (for example, on the Project Exclusions modal).

When a respondent from an excluded project attempts to enter, Research Desk blocks the session before they reach your survey.

## Excluding by time range

For tracking studies that field continuously, you can exclude respondents based on when they completed a prior project — not just whether they participated at any time. This lets you block recent participants while allowing respondents from older waves to re-enter when appropriate.

## Recontacts

Sample recontacts are the inverse of exclusions: instead of blocking prior respondents, you target specific respondents from earlier projects. See [Recontact Respondents](/research-desk/guides/11-recontact-respondents) for the full workflow including RDUD lookup and ORDUD passing.

## Validating exclusions

After configuring exclusions:

1. Confirm the correct parent projects are selected
2. Run an internal test to verify blocked respondents cannot enter
3. Monitor security and termination outcomes during soft launch for unexpected blocks

## Related workflows

* [Creating Projects](/research-desk/guides/01-creating-projects) — Use Duplicate Project for new waves
* [Managing Fieldwork](/research-desk/guides/05-managing-fieldwork) — Monitor traffic after launch