Your Home May Not Be Safe Because Your Smoke Alarms Are in the Wrong Spot

man performing smoke alarm safety check inspection

Are your smoke alarms in the right place? Discover why positioning matters and how it could be the difference between safety and disaster.

Have you heard of the term “dead-air space”? It’s defined as an unventilated area. In the case of your home, many areas and spaces can be considered dead-air space. 

Obviously, if your smoke alarm is installed in dead air space, it might miss the opportunity to shine when it’s needed.

It’s quite common to find smoke alarms installed in dead-air spaces. In fact, we’ve encountered numerous instances of improperly positioned smoke alarms ourselves. Heck, we even serviced a home with no smoke alarms at all!

It’s a common issue, but it’s one that needs to be addressed immediately, especially if you live in a fire-prone area or are renting a property with other lives at risk.

In this article, we explain how those dead-air spaces are formed and why they matter when it comes to smoke alarm positioning.

What is Dead-Air Space?

Dead-air space refers to areas within a building where air circulation is limited or nonexistent. 

They are characterised by limited or stagnant air circulation, which affects their thermal properties. 

NCC 2019 BCA Vol 2,, Pg 270 smoke alarm positioning national construction code australia

Reference: NCC 2019 BCA Vol 2,, Pg 270

When hot air rises, it tends to accumulate in areas where there is little movement or exchange with cooler air. This phenomenon occurs due to the principle of convection, where warm air, being less dense, rises while cooler air sinks.

In these spaces, hot air can become trapped, creating a barrier that prevents smoke from reaching smoke alarms. Due to inadequate airflow around these alarms, their mechanisms fail to activate even when smoke is present nearby.

In the context of buildings, dead-air spaces can be created by various architectural features that impede air movement. For example:

Cathedral Ceilings: These ceilings have a steep slope, creating a large void at the apex. Hot air naturally rises and gets trapped in this upper region, forming a dead-air space.

Corner Junctions: The meeting point between walls and ceilings can create pockets where air movement is restricted, especially in tight corners.

Exposed Joists or Beams: Gaps or channels between exposed structural elements can limit airflow, leading to dead-air spaces.

Understanding these principles helps in recognising the importance of proper ventilation and airflow management within buildings. By minimising dead-air spaces and promoting air circulation, we can improve both fire safety and overall comfort within indoor environments.

Should a smoke alarm safety inspection find that your smoke alarms are placed in dead spaces, you will be required to address it immediately. This is not just a compliance issue. It’s a matter of you and your family’s safety and well-being.

How Does Dead-Air Space Affect Smoke Alarms?

Smoke alarms (most nowadays that are photoelectric) are designed to detect smoke by relying on air passing through their chambers. 

However, in dead-air spaces, the flow of air is restricted, which hinders the smoke’s ability to reach the alarm. This delay in detection can be critical during a fire, as the alarm may not sound in time for occupants to evacuate safely.

Reference: Appliance Fixer Smoke Alarm Safety Check conducted on April 2024 in Port Melbourne, Victoria

The physics behind dead-air spaces impacting smoke alarms lies in the thermal behavior of air. Hot air tends to rise, carrying smoke particles in the case of a fire. 

However, in dead-air spaces, this rising motion is impeded, causing smoke to linger or disperse differently than in areas with proper airflow. As a result, smoke alarms installed in dead-air spaces may not detect smoke promptly or effectively.

Why Is Your Smoke Alarm in a Dead-Air Space?

Many homes have smoke alarms installed in dead-air spaces due to improper positioning during installation. Builders and homeowners may overlook the importance of placing smoke alarms in areas with proper air circulation, leading to compromised safety during a fire emergency.

smoke alarm in dead-air space

Reference: Appliance Fixer Smoke Alarm Safety Check conducted on April 2024 in Port Melbourne, Victoria

Some instances could be attributed to houses designed before the changes were made to the relevant regulation of chapter 2 of the NCC 2019. 

In any case, several factors can contribute to the inadvertent placement of smoke alarms in dead-air spaces:

1. Lack of Awareness: Not all builders may be fully aware of the concept of dead-air spaces and their impact on smoke alarm effectiveness. Without proper education or training on fire safety standards, builders may overlook the significance of correct smoke alarm placement.

2. Architectural Challenges: Certain architectural designs, such as cathedral ceilings or unique room layouts, can pose challenges for smoke alarm installation. Builders may prioritise aesthetics or structural considerations over optimal smoke detection, leading to smoke alarms being placed in less ideal locations.

3. Cost Considerations: In some cases, builders may opt for the most cost-effective installation methods without considering the long-term implications on safety. This can result in smoke alarms being placed in areas prone to dead-air spaces to save time and resources during construction.

4. Limited Guidance: Depending on local regulations and building codes, builders may not receive clear and detailed guidelines regarding smoke alarm placement. Without specific instructions or enforcement, builders may follow generalised practices that do not account for dead-air spaces.

5. Retrofitting Challenges: When retrofitting older buildings with smoke alarms, builders may face challenges in finding suitable locations that meet safety requirements. This can lead to compromises in placement, including positioning alarms in dead-air spaces unintentionally.

6. Client Preferences: In some cases, homeowners may request smoke alarms to be installed in specific locations based on personal preferences or aesthetics. Builders may accommodate these requests without fully evaluating the impact on smoke alarm functionality.

Addressing these challenges requires a collaborative effort between builders, regulatory bodies, and qualified professionals like licensed electricians. 

By raising awareness, providing clear guidelines, and emphasising the importance of proper smoke alarm placement, we can reduce the likelihood of smoke alarms being installed in dead-air spaces and enhance overall fire safety in residential buildings.

Where Should Smoke Alarms Be Placed to Avoid Dead Air Space?

To ensure optimal smoke detection, smoke alarms should be installed on or near the ceiling in areas with good air flow. 

Avoid placing alarms in dead-air spaces such as the apex of cathedral ceilings, tight corners, or areas between exposed joists. Install alarms in open areas where smoke can readily reach the detectors.

smoke alarm positioning

Reference: Appliance Fixer Smoke Alarm Safety Check conducted on April 2024 in Port Melbourne, Victoria

In accordance with the National Construction Code for smoke alarm placement, specific guidelines must be followed to ensure effective detection. Here are the key requirements:

Ceiling Installation:

When installing a smoke alarm on the ceiling, it must be positioned according to the following criteria:

(i) Maintain a minimum distance of 300 mm from the corner junction of the wall and ceiling. This distance helps prevent dead-air spaces that can hinder smoke detection.

(ii) For rooms with sloping ceilings, position the smoke alarm between 500 mm and 1500 mm away from the high point or apex of the ceiling. This range optimises smoke detection in areas prone to air stagnation.

Wall Installation:

If ceiling installation following the above guidelines is not feasible, smoke alarms may be installed on the wall. In such cases:

(a) Position the smoke alarm a minimum of 300 mm away from the corner junction of the wall and ceiling.

(b) Maintain a maximum distance of 500 mm between the smoke alarm and the ceiling at the junction with the wall.

These regulations are designed to enhance smoke alarm performance by avoiding dead-air spaces and ensuring adequate coverage for detecting smoke in various room configurations. 

As a licensed electrician, adhering to these placement requirements is essential for promoting fire safety and compliance with standards in residential properties.

How We Rectify Dead-Air Space Smoke Alarm Placements

From assessment to installation and documentation, this guide provides insights into ensuring optimal safety and compliance in smoke alarm positioning.

Assessment and Identification:

Begin by conducting a thorough assessment of smoke alarm placements in the building. Identify any instances where smoke alarms are located within dead-air spaces, such as near cathedral ceilings, tight corners, or areas with limited airflow.


Document the specific locations and reasons why smoke alarms are deemed to be in dead-air spaces. Include photographs or diagrams to illustrate the problematic areas.

Safety Check and Compliance Review:

Perform a safety check to ensure that smoke alarms are functioning properly despite their placement in dead-air spaces. Review local regulations and building codes to determine compliance requirements for smoke alarm positioning.

Recommendations for Rectification:

Based on the assessment findings, provide detailed recommendations for rectifying dead-air space issues with smoke alarms. This may include:

  • Disconnecting smoke alarms from non-compliant positions.
  • Covering existing holes or mounting points with blank plates or suitable covers to restore the wall or ceiling.
  • Relocating smoke alarms to compliant positions outside of dead-air spaces, ensuring proper distance from walls, corners, and ceiling apexes as per regulatory guidelines.
  • Adjusting mounting heights to optimise smoke detection and airflow around the smoke alarms.

Installation and Relocation Process:

Execute the recommended rectification steps systematically:

  • Disconnect the smoke alarm from its current position carefully, following manufacturer instructions.
  • Seal or cover any holes or openings left by the removed smoke alarm.
  • Install the smoke alarm in the new compliant location, ensuring it meets the specified distance requirements from walls, corners, and ceilings.
  • Test the relocated smoke alarm to ensure proper functionality and connectivity.

Documentation and Reporting:

Provide a detailed report of the rectification process, including:

  • Description of the initial issue (smoke alarms in dead-air spaces).
  • Steps taken for rectification (disconnection, hole covering, relocation).
  • Compliance with safety standards and regulations post-rectification.
  • Testing and verification of the relocated smoke alarms.
  • Recommendations for ongoing maintenance and monitoring of smoke alarm positions.

Client Communication and Education:

Communicate effectively with clients or building occupants regarding the rectification process and the importance of proper smoke alarm placement. Educate them on fire safety best practices, including the role of smoke alarms and the impact of dead-air spaces on their effectiveness.

Breaking Down Smoke Alarm Regulations

Know the Rules: Understand local building rules and standards for smoke alarm placement.

Find the Right Spot: Install smoke alarms where they can hear smoke, like in hallways near bedrooms.

Stay Away from Heat: Avoid placing smoke alarms near stoves or bathrooms where steam can cause false alarms.

Keep Them Powered: Make sure smoke alarms have working batteries or are connected to electricity.

Test Regularly: Press the test button on your smoke alarm monthly to ensure it’s working.

Clean and Maintain: Dust or clean your smoke alarms yearly to keep them sensitive to smoke.

Spread the Word: Share fire safety tips with family members and guests for everyone’s safety.


In conclusion, the placement of smoke alarms plays a crucial role in ensuring the safety of occupants in residential buildings. By understanding the concept of dead-air spaces and their impact on smoke alarm functionality, we can take proactive measures to rectify these issues. 

Through adherence to regulatory guidelines, meticulous installation practices, and ongoing maintenance, we can minimise the risk of smoke alarms being compromised by dead-air spaces. 

Ultimately, prioritising correct smoke alarm positioning contributes significantly to creating safer living environments and protecting lives in the event of a fire emergency. Call us for a smoke alarm inspection today!

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