Centers for Disease Control

and Prevention

National Institute for Occupational 

Safety and Health

Preventing Deaths and Injuries of Fire 

Fighters Working at Basement and 

Other Below-Grade Fires 

Summary

Fire fighters are at significant risk of 

injury or death when fighting fires 

in basements or floors below-grade 

level. The increased risk is due to 

limited entry and egress; working 

above the fire; weakened floor structures; being caught in the fire’s flow 

path; unknown fire load; ventilation 

issues; utility panels, hanging wires, 

meters, and connections; and appliances. These risks can lead to fire 

fighter entrapment from floor collapse, burns, and asphyxiation. Fire 

departments should conduct a complete 360-degree size-up to locate the 

fire, attack the fire externally, and 

reassess fire conditions prior to conducting interior operations. 

Description of Risk 

Fire in a building level that is either partially or completely below the ground 

presents problems for the fire fighter. 

Whether classified as a basement or 

other below-grade area (such as a cellar 

or a multi-level structure built on sloping ground with a single visible point of 

entry at street level), access to a fire 

below-grade may require a descent. 

In many cases, access to a basement or 

other below-grade area is limited to a 

single interior stairway. A fire belowgrade will create a chimney effect when 

the door to the stairway is opened, resulting in a rapidly expanding rush of 

fire from below. Fire fighters attempting 

to descend the stairway will be caught in 

the fire’s flow path and confronted with 

rising heat, fire, and smoke. Conditions 

may immediately become untenable, 

and access to the basement will be lost, 

potentially trapping and/or injuring fire 

fighters below-grade, on the stairway, or 

at the top of the stairs. An interior stairway may also spread fire through the 

structure, endangering fire fighters. 

Fire fighters should not attempt to reach 

a basement fire by an interior stairway. 

Instead, they should work to extinguish 

it through an exterior doorway, window, or other penetration points, and 

then reassess interior conditions. 

Indicators of a 

Basement Fire

Initial indicators can often be observed 

from the exterior of the structure during a 360-degree size-up that locates 

and assesses the fire. During recent 

basement fire experiments conducted 

by NIST and UL, smoke was observed 

coming out of the eaves in buildings 

that were not balloon-frame construction. Researchers suspect this was due 

to the presence of unprotected vertical 

penetrations, pipe chases, and holes for 

cable, phone, internet, and vent pipes. 

These openings will allow smoke and 

heat to move vertically in a structure. 

Internal indicators of a below-grade 

fire include the presence of modest 

heat and dense smoke at the ground or 

first floor level, and the absence of visible fire. Smoke rising from baseboards 

and floor vents on the lower floors and 

banking down on the top floor may 

also indicate a below-grade fire.

A thermal imager should be used during the initial size-up, but fire fighters 

must be properly trained on its use 

and limitations. Test fires have determined that thermal imagers may not 

detect a basement fire when scanning the ground level floor. This is 

because the wood flooring, along 

with carpet and laminate floor covering, tend to insulate and prevent 

heat transfer. Since the ignition time 

of a fire is unknown to the responding fire fighters, the extent of structural fire damage is often unknown, 
and thermal imagers cannot provide a reliable indicator of a 

structural hazard [NIST 2011]. 

Fire fighters should always remember to check a structure 

for a basement or other below-grade area even if the fire appears to be on the ground or higher level. 

Firefighting strategy and tactics for 

basement and other below-grade fires

Basement fires are one of the most challenging situations fire 

fighters encounter. As with all fires, a risk assessment and 

an occupant survivability profile should be conducted to 

evaluate what is at risk—lives or property. Current research 

strongly suggests that before entering the structure, fire attack should be started as soon as possible from exterior positions, applying water directly on the fire through an exterior 

doorway or window, or by penetrations through the basement wall using a penetrating nozzle.

If exterior approaches are not possible, fire suppression 

should be attempted by making penetrations in the floor 

above the basement using a distributor nozzle to knock 

down the fire. The choice to operate above the fire places fire 

fighters at a higher risk of injury or death from structural 

collapse, and therefore, should be considered a last choice 

in the selection of tactics. Fire fighters should initially insert these devices from a safe position (i.e. just inside the entry door). Additional penetrations can be made in the floor 

to move further into the structure if warranted. However, 

structural stability must be assessed before fire fighters proceed out over a floor above a fire. Caution should be taken at all times to not place the fire fighter in that position. 

The structure should be evacuated immediately if structural 

compromise is suspected. 

These approaches have demonstrated a faster drop in temperatures within the fire compartment compared with advancing 

a hoseline inside the basement to the seat of a fire. These approaches also help slow structural compromise in the fire compartment, creating safer conditions for fire fighters, [UL 2013]. 

This rapid lowering of temperatures in the below-grade fire 

compartment is critical from a life safety perspective where 

controlling and knocking down a fire is of utmost importance. Fire fighters must be aware that an active and growing fire in a below-grade compartment is not likely to allow 

for occupant survival, particularly where the only exit is up a 

stairway. However, survival might be possible with the application of water into the below grade compartment from the 

exterior because of the rapid cooling, making search and rescue activities feasible.

If a decision is made that it is necessary to enter the basement or below-grade area for fire attack or search/rescue, an 

interior fire attack strategy with properly coordinated ventilation is necessary to ensure fire fighter safety. In many cases, the preferred method of attacking this type of fire is from 

the same level. An example would be using an exterior access point such as a walk-out doorway or window. While this 

fire attack method provides quick access, fire fighters should 

always use caution. Any active fire will have damaged the 

structural integrity of the floor system above them, creating 

a collapse risk. 

Basements are known for very limited ventilation possibilities. In the absence of built-in basement vents, such as exterior doors or windows, heat and smoke from basement fires 

can quickly spread upward throughout the building. This is 

especially true in balloon-frame construction and structures 

without vertical fire stops between floors. Modern construction also contains many vertical penetrations. Exposed and 

unprotected construction features below and through floors 

(such as laundry chutes, stud channels, and duct work) may 

contribute to rapid fire, heat, and smoke spread, increasing 

collapse potential. 

If a ventilation opening is made in an area away from where 

the fire fighters entered, smoke and heat may be pulled away 

from the attack crew towards the ventilation opening. This 

will allow the crew to better attack the fire. However, a backup hose line should be in place to protect the attack crew 

[IFSTA 2013]. 

Case Study

On June 2, 2011, a 48-year-old male career lieutenant and a 

53-year-old male fire fighter/paramedic died in a multilevel residential structure fire while searching for the seat of 

the fire. The structure was built on a steeply sloped hillside. 

The fire floor was one floor below street level. 

The lieutenant and a fire fighter/paramedic on the firstarriving crew, Engine 26 (E‒26), noticed light smoke as they 

advanced a hose line through the street-level front door on 

Side A. Minutes later, the incident commander (IC) tried 

contacting them over the radio but received no response. 

A battalion chief (BC) assigned to the fire attack group followed the hose line through the door and spoke to the E‒26 

crew near the stairway to the below-grade main living areas. 

The lieutenant told the BC that the fire must be a floor below them. The BC stated the fire would be attacked from the 

structure’s Side B and exited the front door. The E‒26 crew 

did not follow. 

A few minutes later, the IC again tried to contact the E‒26 

crew via radio with no response. The BC went to the Side 

B door (located on the outside, one floor below street level) 

and forced the door with another hose line crew, Engine 11 

(E‒11). The E‒11 crew immediately felt a blast of heat from 
the fully involved basement area and proceeded to knock 

down the fire (Figures 1 and 2). 

Figure 1. Image from computerized fire model showing 

flow path and conditions in interior stairwell of the 

structure. Photo by NIST.

Figure 2. Fire is visible at the rear balcony (Side C). 

Stairs seen on the right side of the structure were used 

by fire fighters to enter the structure at Side B. Photo by 

the fire department.

At about this time, a crew from Engine 24 (E‒24) followed 

the E‒26 crew’s hose line through the street-level front door. 

In zero visibility conditions, the E‒24 crew found the two 

downed members of E‒26 in the basement. Both members 

were removed from the structure, and medical attention was 

initiated before they were transported to a local hospital.

The lieutenant was pronounced dead and the fire fighter/

paramedic died two days later. Contributing factors that led 

to the fatalities included the below-grade fire within a house 

on a steep hillside, uncoordinated ventilation, ineffective 

size-up, ineffective fire ground communications, and situational reporting [NIOSH 2011].

Additional basement fire hazards, such as fire fighters falling through fire-weakened floors, wind driven fires, and 

chimney effect of internal stairways are highlighted by the 

following NIOSH investigation reports: (1) F2008-08: Volunteer Fire Lieutenant Killed While Fighting a Basement 

Fire—Pennsylvania; (2) F2008-09: A Career Captain and a 

Part-time Fire Fighter Die in a Residential Floor Collapse–

Ohio; (3) F2014-09:Lieutenant and Fire Fighter Die and 13 

Fire Fighters Injured in a Wind-Driven Fire in a Brownstone—Massachusetts; and (4) F2014-25: Career Female 

Fire Fighter Dies after Becoming Lost and Running out of 

Air in a Residential Structure Fire—Pennsylvania.

Controls

To minimize the risks of working basement and other belowgrade fires, NIOSH recommends that fire departments take 

the following precautions.

Pre-Incident:

 Develop and enforce standard operating procedures 

(SOPs) for safely attacking fires in basements and other 

below-grade structures.

 Ensure that an incident management system is used at 

all incidents including a personnel accountability system. Also, ensure that all members involved in firefighting operations wear full personal protective equipment, 

including an SCBA with integrated PASS device, and are 

provided a portable radio.

 Provide fire fighters with practical hands-on training for 

identifying indicators of basement and other below-grade 

fires, heat and smoke movement through ventilation, fire 

location, and a safe exterior and interior firefighting operations.

 Conduct pre-planning of first due response areas to identify construction types, building access, and below-grade 

areas and structures. 

Incident:

 Ensure a thorough initial 360-degree size-up is conducted, and a crew is assigned to Side C.

 Use a thermal imager as part of a 360-degree size-up to assist in determining the fire location.

 Ensure the first arriving officer and/or incident commander completes an initial survivability profile and risk assessment with continuous monitoring of risk versus gain.
 Ensure the strategy and incident action plan is communicated to all on-scene and responding personnel before a 

decision is made to enter a building.

 Ensure the incident commander assigns a safety officer 

who is trained to recognize hazards associated with basement and other below-grade fires. 

 At any point when risk outweighs gain, especially for property only, the incident commander should initiate a defensive strategy. 

If the risk assessment determines interior operations are necessary and feasible, take the following steps:

 Prior to conducting interior fire attack operations, ensure at 

least one rapid intervention crew is on site with necessary 

equipment to respond to missing or trapped fire fighters. 

 Do not attempt to attack the basement fire from an interior stairway. 

 Before entry, ensure a thorough 360-degree size-up has 

been conducted that determines fire location, primary and 

alternate ingress and egress points, strategy and incident 

action plan (tactics), and communicate this information to 

all personnel responding or on scene.

 Use a thermal imager to aid in locating fires burning below or between floor systems but understand its use and 

limitations when trying to determine structural integrity. Scan over baseboards and vents. If possible and safe, a 

floor should be inspected from below prior to operating on 

it [Kerber et al. 2012]. 

 Secure an uninterrupted water supply that will provide an 

adequate and necessary water flow needed for complete 

fire extinguishment. 

 Perform an exterior offensive attack by flowing water onto 

the fire from an exterior basement door, window, or by 

breaching exterior basement walls and then reassess conditions before advancing a hose line and/or looking for interior extension. 

 Stretch a back-up line to protect the primary hose line 

crew’s egress route and additional hose lines to protect secondary entry and egress points such as basement windows 

or doors.

 Be aware of how ventilation affects fire behavior and coordinate ventilation with firefighting operations so that the 

flow path is appropriately identified and controlled.

 Fire fighters should keep the wind at their back and stay 

upwind of the fire.

 Fire departments should use all available options to prevent fire fighters from working on unrated floor assemblies 

above a fire [Madrzykowski 2013].

 If necessary, make penetrations in the floor above the 

basement using a distributor nozzle to knock down the 

fire. Fire fighters should initially insert these devices from 

a safe position (i.e. just inside the entry door). Additional 

penetrations can be made in the floor to move further into 

the structure if warranted, but only if the floor is stable.

 Immediately evacuate a structure if a floor above a fire has 

been weakened. If possible, use an alternate exit route to 

avoid crossing over a weakened area.

 Use defensive overhaul procedures after fire extinguishment in structures containing fire damaged floor systems 

and stairways.

Post Incident:

Every fire department should conduct a post incident analysis for significant incidents, especially basement or belowgrade fires.

Every fire department should periodically update their community risk assessment program and pre-incident planning 

process based on recommendations from post incident analysis reports.

In addition, the best protections for fire fighters and occupants, as well as for structures, are preventive measures such 

as (1) smoke alarms; (2) equipping basements with automatic 

sprinkler systems; (3) covering the underside of floor systems 

with a fire-resistant membrane; (4) not using a basement or 

other below-grade structure in a manner that conflicts with the 

code it was designed to, and; (5) including egress points such as 

windows or walk-out doorways that are accessible.

Acknowledgments

The principal contributors to this publication were Timothy Merinar, Stacy Wertman and Murrey Loflin, National Institute for Occupational Safety and Health, Fire Fighter Fatality Investigation and Prevention Program; and Fire Chief 

Gary Morris, International Association of Fire Chiefs; Safety, 

Health, and Survival Section.

References

IFSTA [2013]. Essentials of fire fighting, 6th ed. Oklahoma 

State University. Stillwater, OK: Fire Protection Publications. International Fire Service Training Association.

NIOSH [2011]. A career lieutenant and fire fighter/paramedic 

die in a hillside residential house fire—California. Cincinnati, OH: U.S. Department of Health and Human Services, 

Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, FACE Report 

2011-13, www.cdc.gov/niosh/fire/reports/face201113.html

NIST [2011]. Examination of the thermal conditions of a 

wood floor assembly above a compartment fire. https://

www.nist.gov/el/fire-research-division-73300/firegov-fireservice/examination-thermal-conditions-wood-floor

Kerber S, Madrzykowski D, Dalton J, Backstrom R [2012]. Improving fire safety by understanding the fire performance of 

engineered floor systems and providing the fire service with 

information for tactical decision making. Northwood, IL: 

Underwriters Laboratories. 
Madrzykowski D [2013]. Fire dynamics: the science of fire 

fighting. International Fire Service Journal of Leadership 

and Management, Volume 7. Fire Protection Publications/

IFSTA.

UL [2013]. Innovating fire attack tactics. Underwriters Laboratories. https://www.ul.com/global/documents/newscience/article/firesafety/NS_FS_Article_Fire_Attack_Tactics.pdf

Training Materials and Additional 

Sources of Information

Underwriters Laboratories (UL) maintains a website dedicated to fire fighter safety. https://ulfirefightersafety.org/

UL also maintains a website dedicated to the risks of modern 

fire behavior. http://modernfirebehavior.com/

The National Institute of Standards and Technology (NIST) 

Building and Fire Research Laboratory maintains a website with links to publications on a number of fire safety topics and research. https://www.nist.gov/el/fire-research-division-73300

Jerrard J [2012]. UL Basement fire study. Fire Rescue 7(8). 

http://www.firerescuemagazine.com/articles/print/volume-7/issue-8/firefighter-safety/ul-basement-fire-study.

html

Kirby M [2013]. Basement fire tactics. Fire rescue 8(8). http://

www.firerescuemagazine.com/articles/print/volume-8/

issue-8/strategy-and-tactics/basement-fire-tactics.html

NIOSH [2009a]. Volunteer fire lieutenant killed while fighting a basement fire—Pennsylvania. https://www.cdc.gov/

niosh/fire/pdfs/face200808.pdf

NIOSH [2009b]. A career captain and a part-time fire fighter 

die in a residential floor collapse—Ohio. https://www.cdc.

gov/niosh/fire/pdfs/face200809.pdf

NIOSH [2016]. Lieutenant and fire fighter die and 13 fire 

fighters injured in a wind-driven fire in a brownstone—

Massachusetts. https://www.cdc.gov/niosh/fire/pdfs/

face201409.pdf

NIOSH [2017]. Career female fire fighter dies after becoming lost and running out of air in a residential structure 

fire—Pennsylvania. https://www.cdc.gov/niosh/fire/pdfs/

face201425.pdf

For More Information

More information about the NIOSH Fire Fighter Fatality Investigation and Prevention Program can be found at 

https://www.cdc.gov/ niosh/fire/.

A complete list of NIOSH fire fatality reports can 

be found at https://wwwn.cdc.gov/NIOSH-firefighter-face/Default.cshtml?state=ALL&Incident_

Year=ALL&Submit=Submit.

To receive documents or other information about occupational safety and health topics, contact NIOSH at

Phone: 1-800-CDC-INFO (1-800-232-4636)

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Preventing Deaths and Injuries of Fire Fighters 

Working at Basement and Other Below-Grade Fires

DOI: https://doi.org/10.26616/NIOSHPUB2018154

DHHS (NIOSH) Publication No. 2018-154

July 2018