---
key: create-a-suppression-window
title: Mute alerts during maintenance
audience: staff
section: critical-alerts
routes: ["/critical-alerts/suppressions", "/critical-alerts/suppressions/new"]
permissions: ["critical_alerts.suppressions.create"]
features: ["critical_alerts.core"]
since: 0.0.1
updated: 0.0.1
status: published
summary: Create a suppression window so planned maintenance on a site or system does not call anyone, and preview exactly which rules and incidents it affects.
keywords: [mute, silence, maintenance window, planned outage, stop alerts, quiet, pause alarms, snooze a source, downtime]
related: [end-or-archive-a-suppression-window, create-a-critical-alert-rule, critical-alerts-guide]
---

In the sidebar, open **Critical Alerts**, then **Setup**, then **Suppressions**. The page address is `/critical-alerts/suppressions`.

A suppression window is a start time, an end time and a scope. While it is in effect, matching signals are still recorded, but Nova does not call, text or email anyone about them.

## Before you start

- Your admin has to give your role permission to create suppression windows.
- Know the scope: which sources, rules, source types or severities the work touches. A window with no scope mutes everything.

## Steps

1. Press **New suppression**. The **Create suppression window** drawer opens.
2. Type a **Name** and a **Reason** such as "Boiler replacement at Main St". The **Key** fills in from the name.
3. Set **Starts at** and **Ends at**. Press **Now** beside either field to use the current time, or pick a length under **Window**: **1hr**, **1 day**, **1 week** or **1 month**. **Sync** lines the end up with the start again so the window keeps its length.
4. Choose the scope: **Sources**, **Rules**, **Source types** and **Severities**. Leave a field empty to mean "any".
5. Under **Policy mode**, keep the default, which holds back delivery, or choose the mode that only notes the suppression on the incident and still delivers.
6. Under **Bypass severities**, pick any severities that should still get through, for example **Critical**.
7. Press **Preview impact**. Nova shows how many sources, rules, active incidents and suppressed incidents the window would touch, plus any warnings.
8. Press the create button at the bottom of the drawer (it reads "Create suppression"). The window takes effect at its start time.

## What you see

- Each row shows the window's state (upcoming, active, expired or archived), its scope, the reason, and the start and end times.
- The **Filters** button narrows by **Status** and **Visibility**; **Visibility** hides archived windows unless you change it.
- **Change reason** in the drawer is a note kept with this edit in the audit history.
- **Advanced scope JSON** and **Advanced policy JSON** appear only for roles allowed to edit them. Everyone else sees a note that advanced editing is hidden for their role.

## If something looks different

- An alert still came through during the window: its severity is in **Bypass severities**, or its rule or source is outside the scope. Press **Preview impact** to check.
- The window did not start: its **Status** is draft or disabled. See [[end-or-archive-a-suppression-window]].
- **New suppression** is greyed out: your role cannot create suppression windows.

[[route:/critical-alerts/suppressions|Open Suppressions]]