NISTIR 7412 

Evaluating Positive Pressure Ventilation In Large Structures: High-Rise 

Pressure Experiments 

Stephen Kerber 

Daniel Madrzykowski 

David Stroup 

U.S. Department of Commerce 

Technology Administration 

Building and Fire Research Laboratory 

National Institute of Standards 

and Technology 

Gaithersburg, MD 20899 

1

NISTIR 7412 

Evaluating Positive Pressure Ventilation In Large Structures: High-Rise 

Pressure Experiments 

Stephen Kerber 

Daniel Madrzykowski 

David Stroup 

U.S. Department of Commerce 

Technology Administration 

Building and Fire Research Laboratory 

National Institute of Standards 

and Technology 

Gaithersburg, MD 20899

March 2007 

Department of Homeland Security 

Michael Chertoff, Secretary 

Preparedness Directorate 

George W. Foresman, Under Secretary 

 for Preparedness

United States Fire Administration 

Charlie Dickinson, Acting Administrator

U.S. Department of Commerce

Carolos M. Gutierrez, Secretary

Technology Administration

Robert Cresanti, Under Secretary

Of Commerce for Technology

National Institute of Standards and 

Technology

William Jeffrey, Director
iii

Table of Contents 

List of Tables ................................................................................................ iv

List of Figures............................................................................................... iv

1.0 Introduction ........................................................................................ 7

2.0 Experimental Overview ................................................................... 10 

 2.1 Structure......................................................................................11 

 2.2 Instrumentation..............................................................................15 

3.0 Experimental Procedure.................................................................. 20

4.0 Results................................................................................................ 25

4.1 Stairwell Differential Pressure................................................................................ 25 

4.1.1 Optimal fan placement at stairwell door (D2) ................................................ 25 

4.1.2 Optimal fan placements at ground floor entrance (D1) .................................. 28 

4.1.3 Multiple fans at ground floor entrance (D1)................................................... 30 

4.1.4 Multiple fans at stairwell doorway (D2)......................................................... 33 

4.1.5 Open doors in the stairwell ............................................................................. 35 

4.1.6 Multiple fans at multiple ground level doors.................................................. 36 

4.1.7 Fans located inside the building...................................................................... 37 

4.1.8 1.2 m (46 in) trailer mounted fan at ground floor entrance ............................ 39 

4.1.9 Further analysis of fans located inside the building........................................ 40 

4.1.10 Fans at ground level and in the building with the bulkhead 

door open .................................................................................................................. 42 

4.1.11 Fans at ground level and in the building with the roof hatch open............... 45 

4.1.12 Ground level doorway sealed / Fan efficiency .............................................. 48 

4.1.13 Other types of fans at the ground level stairwell door................................... 49 

4.1.14 Fans and a hovercraft at ground floor entrances (D1 and D3)....................... 51 

4.2 Stairwell Temperature....................................................................................... 53 

4.3 Weather............................................................................................................. 54 

4.4 Carbon Monoxide ............................................................................................. 57 

4.5 Sound Levels..................................................................................................... 62 

5.0 Uncertainty........................................................................................ 63

6.0 Discussion .......................................................................................... 65

7.0 Future Research................................................................................ 67

8.0 Conclusions........................................................................................ 68

9.0 References.......................................................................................... 70

10.0 Acknowledgments ............................................................................. 72
iv

List of Tables 

Table 1. NFPA 92A Minimum Design Pressure Differences Across Smoke Barriers...... 9 

Table 2. Experimental overview description ................................................................... 10 

Table 3. Door and hatch dimensions................................................................................ 12 

Table 4. 0.4 m (16 in) fan setback/angle analysis at ground floor stairwell door............ 20 

Table 5. 0.5 m (21 in) fan setback/angle analysis at ground floor stairwell door............ 21 

Table 6. 0.7 m (27 in) fan setback/angle analysis at ground floor stairwell door........... 21 

Table 7. Best setback/angles at ground floor entrance door ............................................ 22 

Table 8. Multiple fans at ground floor entrance door (series and parallel 

configurations) .......................................................................................................... 22 

Table 9. Multiple fans at stairwell door........................................................................... 22 

Table 10. Stairwell door(s) open configuration(s)........................................................... 22 

Table 11. Fans at multiple ground floor doors................................................................. 23 

Table 12. Fans in the structure......................................................................................... 23 

Table 13. 46” trailer mounted fan at ground floor entrances........................................... 23 

Table 14. Fans in the structure setback configurations.................................................... 23 

Table 15. Roof door ventilation through 29th floor.......................................................... 24 

Table 16. Roof hatch ventilation through 29th floor ........................................................ 24 

Table 17. Roof hatch ventilation through 28th floor ........................................................ 24 

Table 18. Ground floor doorway sealed, Fan efficiency ................................................. 25 

Table 19. Other fan types at ground floor stairwell door................................................. 25 

Table 20. Hovercraft at ground floor entrance................................................................. 25 

Table 21. Noise Scale ...................................................................................................... 63 

Table 22. Uncertainty....................................................................................................... 64

List of Figures 

Figure 1. Two common PPV fans...................................................................................... 9 

Figure 2. Conical air jet produced by PPV [14]............................................................... 10 

Figure 3. Front (Side A) and left side (Side B) of the building (left photo) and rear 

(Side C) ..................................................................................................................... 12

Figure 4. Ground Floor Plan ............................................................................................ 13 

Figure 5. Floors 2-13 floor plan....................................................................................... 13 

Figure 6. Floor 14-28 floor plan. ..................................................................................... 14 

Figure 7. Floor 29 and roof floor plan. ............................................................................ 14 

Figure 8. Instrumentation layout diagram (P-pressure, T-temperature, CO-carbon 

monoxide,.................................................................................................................. 16 

Figure 9. Differential pressure set-up .............................................................................. 17 

Figure 10. Thermocouple location................................................................................... 17 

Figure 11. Carbon monoxide meter ................................................................................. 18 

Figure 12. Ground weather station................................................................................... 18 

Figure 13. Roof weather station....................................................................................... 19 

Figure 14. Sound meter.................................................................................................... 19 

Figure 15. Fans placed at stairwell doorway, (a) 0.4 m (16 in), (b) 0.5 m (21 in), 

(c) 0.7 m (27 in) ....................................................................................................... 26 

Figure 16. Stairwell pressures created by a 0.4 m (16 in) fan ......................................... 27 

Figure 17. Stairwell pressures created by a 0.5 m (21 in) fan ......................................... 27 

Figure 18. Stairwell pressures created by a 0.7 m (27 in) fan ......................................... 28 

Figure 19. Fan placed at ground level doorway (D1) ...................................................... 29 
v

Figure 20. Stairwell pressures from fans blowing into D1 .............................................. 29 

Figure 21. Fans placed at ground floor entrance (D1), a. 2 fans in series, b. 2 fans in 

V-shape, c. 2 fans in V-shape (top/bottom), d. 3 fans in V-shape w/center, 

e. 3 fans in series....................................................................................................... 31 

Figure 22. Stairwell pressures from multiple 21 in. fans at D1 ....................................... 32 

Figure 23. Stairwell pressures from multiple 27 in. fans at D1 ....................................... 32 

Figure 24. Multiple fans in series at stairwell doorway, a. 1.2 m and 2.4 m, 

b. 1.2 m, 2.4 m and 3.7 m ......................................................................................... 33 

Figure 25. Stairwell pressures from 0.5 m (21 in) fans in series at D2 ........................... 34 

Figure 26. Stairwell pressures from 0.7 m (27 in) fans in series at D2 ........................... 34 

Figure 27. Stairwell pressure with doors open................................................................. 35 

Figure 28. Fans placed at multiple doors, a. Fans at D2 and D3, b. Fans at D1.............. 36 

Figure 29. Stairwell pressures with multiple fans at multiple doors................................ 37 

Figure 30. Fan positioned in the building ........................................................................ 38 

Figure 31. Stairwell pressures with fans inside the building ........................................... 38 

Figure 32. Trailer mounted fan at stairwell door. ............................................................ 39 

Figure 33. Stairwell pressures made by the 1.2 m (46 in) fan at the stairwell door. ....... 40 

Figure 34. Fans locations in the stairwell ........................................................................ 41 

Figure 35. Stairwell pressures created with fans at the 12th floor................................... 42 

Figure 36. Stairwell pressures created by 0.5 m (21 in) fans with the 29th floor and 

bulkhead door open................................................................................................... 43 

Figure 37. Stairwell pressures created by 0.7 m (27 in) fans at the ground level with 

the 29th floor and bulkhead door open. .................................................................... 44 

Figure 38. Stairwell pressures created by 0.7 m (27 in) fans on the 12th floor with 

the 29th floor and bulkhead door open. .................................................................... 45 

Figure 39. Stairwell pressures created by a single fan with the 28th floor and roof 

hatch open. ................................................................................................................ 46 

Figure 40. Stairwell pressures created by multiple fans with the 28th floor and roof 

hatch open. ................................................................................................................ 47 

Figure 41. Stairwell pressures created by fans in the building with the 28th floor 

and roof hatch open................................................................................................... 47 

Figure 42. Stairwell pressures created by a 0.5 m (21 in) fan with the doorway 

sealed and with the fan setback................................................................................. 48 

Figure 43. Other types of fans and configurations. (a) 2 – 21 in. fans side by side 

(b) 2 – 21 in. fans in series (c) 24 in. and 31 in. fans side by side (d) 21 in. 

Toledo truck fan........................................................................................................ 50 

Figure 44. Pressures created by other manufacturer’s fans in various configurations .... 51 

Figure 45. Hovercraft positioned at ground floor entrance (D3)..................................... 52 

Figure 46. Stairwell pressures created by fans and hovercraft positioned at D1 

and D3....................................................................................................................... 52

Figure 47. Stairwell temperatures.................................................................................... 53 

Figure 48. Average temperatures..................................................................................... 55 

Figure 49. Average wind speed. ...................................................................................... 55 

Figure 50. Average wind direction. ................................................................................. 56 

Figure 51. Relative humidity. .......................................................................................... 56 

Figure 52. Barometric pressure........................................................................................ 57 

Figure 53. Carbon monoxide levels for experiments 2 through 54. ................................ 59 

Figure 54. Carbon monoxide levels for experiments 56 through 100. ............................ 60 

Figure 55. Carbon monoxide levels for experiments 101 through 139. .......................... 61 

Figure 56. Carbon monoxide levels for experiments 150 through 160. .......................... 62 
6

Evaluating Positive Pressure Ventilation In Large Structures: High-rise Pressure 

Experiments 

Stephen Kerber 

Daniel Madrzykowski 

David Stroup 

Abstract 

One hundred and sixty experiments were conducted in a thirty-story vacant office building in 

Toledo, Ohio to evaluate the ability of fire department positive pressure ventilation (PPV) fans to 

pressurize a stairwell in a high-rise structure in accordance with established performance metrics 

for fixed stairwell pressurization systems. Variables such as fan size, fan angle, setback distance, 

number of fans, orientation of fans, number of doors open and location of vents open were varied 

to examine capability and optimization of each. Fan size varied from 0.4 m (16 in) to 

1.2 m (46 in). Fan angle ranged from 90o

 to 80o. The setback distance went from 0.6 m (2 ft) to 

3.6 m (12 ft). One fan to as many as nine fans were used which were located at three different 

exterior locations and three different interior locations. Fans were oriented both in series and in 

parallel configurations. Doors throughout the building were opened and closed to evaluate the 

effects. Finally a door to the roof and a roof hatch were used as vent points. The measurements 

taken during the experiments included differential pressure, air temperature, carbon monoxide, 

metrological data and sound levels. 

PPV fans utilized correctly can increase the effectiveness of fire fighters and survivability of 

occupants in high-rise buildings. In a high-rise building it is possible to increase the pressure of 

a stairwell to prevent the infiltration of smoke if fire crews configure the fans properly. 

Although many factors contribute and need to be considered for effective PPV operations, 

properly configured PPV can achieve stairwell pressures that are high enough to meet or exceed 

the performance metrics for fixed smoke control systems. 

Disclaimer 

Certain trade names and company products are mentioned in the text or identified in an 

illustration in order to specify adequately the experimental procedure and equipment used. In no 

case does such identification imply recommendation or endorsement by the National Institute of 

Standards and Technology, nor does it imply that the products are necessarily the best available 

for the purpose. 
7

1.0 Introduction 

According to the National Fire Protection Association (NFPA) Life Safety Code, a high rise 

building is “a building greater than 23 m (75 ft) in height measured from the lowest level of fire 

department vehicle access to the floor of highest occupiable story” [1]. In 1910, the New York 

City Fire Department Chief, Edward Croker informed the New York State Assembly that the fire 

department could not successfully combat a fire in a building greater than 7 stories tall. Three 

months later a fire in the Triangle Shirtwaist Company, which occupied the top three floors of a 

ten story building in New York City, resulted in the deaths of 146 people [2]. As a result of that 

fire, many improvements were made in the life safety of buildings. 

Between 1985 and 2002 there have been approximately 385,000 fires in high-rise buildings 

greater than seven stories. These fires resulted in 1600 civilian deaths and more than 20,000 

civilian injuries *[3]. Smoke is a major problem in high-rise fires as it travels to building 

locations remote from the fire and causes a serious life hazard. Stairwells may fill with smoke, 

hindering evacuation and enabling the spread of smoke to other floors of the building. 

Fires in high-rise buildings can produce severe challenges for fire departments. Operations that 

are normally considered routine, such as fire attack, evacuating occupants and ventilation can 

become very difficult in high-rises. Smoke and hot gases in the stairwells and the corridors of 

high rise buildings complicate rescue and firefighting operations. Between 1977 and 2005, 

20 fire fighters died from traumatic injuries suffered in high-rise fires in the United States *[4]. 

Fire fighters often rely upon built-in fire protection systems to help control a high-rise fire and 

protect building occupants. In many cases the buildings do not have the necessary systems or the 

systems fail to operate properly. This has created situations where even the most experienced 

and best equipped fire departments could not readily control the fire [5-8]. Many high-rise 

incidents have resulted in fire fighter fatalities due to disorientation, running out of air, or 

changes in wind conditions [7, 9-11]. 

An effective fire protection system for preventing major high-rise fires is an automatic sprinkler 

system. Not all high-rise buildings have automatic sprinkler systems and even when they 

function as intended there is still a serious life hazard created by smoke production and spread. 

In order to limit the smoke hazard, ventilation systems have been utilized. In particular, 

pressurization smoke control systems have been incorporated into high-rise buildings since the 

1970s. 

In 1972, the Brooklyn Polytechnic Institute collaborated with the Fire Department of New York 

City [12] to conduct a series of fire experiments in a 22 story office building to evaluate the 

effectiveness of pressurization smoke control. Materials representative of fuels that would be in 

an office building were burned and it was demonstrated that pressurization could maintain 

tenable exits during a large unsprinklered fire. Subsequent experiments have been done to 

*Not including the World Trade Center losses of September 11, 2001. 

 
8

examine the ability of pressurization to prevent smoke from entering paths of smoke spread such 

as stairwells, elevator shafts and areas outside of the fire origin. All of these experiments 

demonstrated that pressurization could control smoke from large unsprinklered fires. 

In 1986, the NFPA began to provide guidance for smoke management systems. NFPA 92A [13] 

was developed to address smoke control utilizing barriers, airflows and pressure differences so as 

to confine the smoke of a fire to the zone of fire origin and thus maintain a tenable environment 

in other zones. Guidance for minimum pressures that are able to inhibit the flow of smoke into 

the stairwell is provided in Table 1. The values in the table for nonsprinklered buildings are 

minimum design pressures developed for gas temperatures of 927 oC (1700 oF) next to the smoke 

barrier with a 7.5 Pa (0.03 in. water) safety factor added. These criteria for fixed stairwell 

pressurization systems provides a metric to assess the ability of fire department positive pressure 

ventilation (PPV) fans to provide a smoke-free escape route for occupants and a smoke-free 

staging area for fire fighters. 

NFPA 92A also states that a smoke control system should be designed to maintain the minimum 

design pressure differences under likely conditions of stack effect and wind. Pressure 

differences produced by smoke-control systems tend to fluctuate due to the wind, fan pulsations, 

door opening, doors closing, and other factors. Short-term deviations from the suggested 

minimum design pressure difference might not have serious effect on the protection provided by 

a smoke-control system. There is no clear-cut allowable value of this deviation. It depends on 

the tightness of doors, tightness of construction, airflow rates, and the volumes of spaces. 

Intermittent deviations up to 50 % of the suggested minimum design pressure difference are 

considered tolerable in most cases [13]. 

Positive pressure ventilation is a technique used by the fire service to remove smoke, heat and 

other combustion products from a structure. This allows the fire service to perform tasks in a 

more tenable environment. PPV fans are commonly powered with an electric or gasoline engine 

and range in diameter from 0.30 m to 0.91 m (12 in to 36 in) (Figure 1). More recently, fans up 

to 2.1 m (84 in) have been manufactured and mounted on trucks and trailers. Typically, a PPV 

fan is placed about 1.2 m to 3.0 m (4 ft to 10 ft) outside the doorway of the structure. It is 

positioned so that the conical jet of air produced by the fan extends beyond the boundaries of the 

opening (Figure 2). With the doorway within the air jet, pressure inside the structure increases. 

An exhaust opening in the structure, such as an opening in the roof or an open window, allows 

the air to escape due to the difference between the inside and outside air pressure. As a result of 

the introduced air, the smoke, heat and other combustion products are pushed out of the structure 

and replaced with ambient air. 

Another use of PPV is to increase the pressure in a portion of a structure by not providing a vent 

location. This increase in pressure, if adequate, will prevent smoke flow to an area to be 

protected. This may be most useful in larger structures such as schools, hospitals and high-rise 

buildings. In a high-rise building it is possible to increase the pressure of a stairwell to prevent 

the infiltration of smoke if the fans are properly configured. This study evaluates the variables 
9

associated with the fire department’s implementation of PPV fans to achieve stairwell 

pressurization using fixed smoke control performance metrics. 

Table 1. NFPA 92A Minimum Design Pressure Differences Across Smoke Barriers 

Building Type Ceiling Height Design Pressure Difference 

 m (ft) Pa (in. water) 

Sprinklered Any 12.5 (0.05) 

Nonsprinklered 2.7 (9) 24.9 (0.1) 

Nonsprinklered 3.6 (11.7)* 28.6 (0.11)* 

Nonsprinklered 4.6 (15) 34.9 (0.14) 

Nonsprinklered 6.4 (21) 44.8 (0.18) 

* Values for these experiments 

Figure 1. Two common PPV fans 
10

Figure 2. Conical air jet produced by PPV [14] 

2.0 Experimental Overview 

One hundred and sixty experiments were conducted to evaluate the ability of fire department 

positive pressure ventilation fans to pressurize a stairwell in a high-rise structure. The stairwell 

was pressurized in accordance with performance metrics previously established for fixed 

stairwell pressurization systems. Table 2 displays a broad overview of experimental groups used 

to analyze the effectiveness of PPV fans. Variables such as fan size, fan angle, setback distance, 

number of fans, orientation of fans, number of doors open and location of vents open were varied 

to examine capability and optimization of each. Fan size varied from 0.4 m (16 in) to 

1.2 m (46 in). The face of the fan was placed perpendicular to the ground and also tilted 

backward so that the face was at angles of 85 degrees and 80 degrees to the ground as the fan 

was tilted backward. The setback distance ranged from 0.6 m (2 ft) to 3.6 m (12 ft). Setback 

distance was measured from the exterior face of the doorway to the face of the fan. Between one 

and nine fans were used and fans were located at three different exterior locations and three 

different interior locations. Fans were oriented in both series and in parallel. Doors throughout 

the building were opened and closed to evaluate the pressure change. Finally a door to the roof 

and a roof hatch were used as vent points to evaluate the effects of vent size and location. 

 Table 2. Experimental overview description 

Experiments Overview Description 

1-18 0.4 m (16 in) fan setback/angle analysis at ground floor stairwell door 

19-36 0.5 m (21 in) fan setback/angle analysis at ground floor stairwell door 

37-54 0.7 m (27 in) fan setback/angle analysis at ground floor stairwell door 

56-61 Best setback/angles at ground floor entrance door 

62-71 Multiple fans at ground floor entrance door (series and parallel configurations) 

72-77 Multiple fans at stairwell door 

78-84 Stairwell door(s) open configuration(s) 

85-86 Fans at multiple ground floor doors 

87-91 Fans in the structure 

92-100 1.2 m (46 in) trailer mounted fan at ground floor entrances 

101-109 Fans in the structure setback configurations 
11

110-122 Roof door ventilation through 29th floor 

123-127 Roof hatch ventilation through 29th floor 

128-136 Roof hatch ventilation through 28th floor 

137-139 Ground floor doorway sealed, Fan efficiency 

150-159 Other fan types at ground floor stairwell door 

160 Hovercraft at ground floor entrance 

2.1 Structure 

These experiments were conducted in a thirty-story vacant office building in Toledo, 

Ohio. The building was constructed in 1969 with an overall height of 121.9 m (400 ft) 

and an overall floor area of 40,645 m2

 (437,500 ft2). Each floor was approximately 

48.8 m (160 ft) wide by 25.9 m (85 ft) deep with a ceiling height of 3.6 m (11.7 ft). The 

ground floor was taller and had a ceiling height of 6.3 m (20.7 ft). Figure 3 shows all 

four sides of the building. Two mechanical floors are located between floors 13 and 14. 

Three exterior doors were utilized during the experiments, the single door directly into 

the stairwell (D2), the double door on the right side of Side A (D1), and the double door 

on the left side of Side A (D3) (figure 4). Door sizes are in Table 3. The rotary doors 

inside of D1 and D3 were open for the duration of the experiments. All other doors to the 

ground floor were closed at all times. The door to the stairwell on side A (S1) remained 

open during all of the experiments and led to the stairwell that was used for the 

experiments. 

A square stairwell in center of side A opened to the basement and remained open during 

the experiments. The basement was 1540 m2

 (16,570 ft2) with a 3.6 m (11.7 ft) ceiling. 

The second stair that accessed the basement was located near the rotary door on side C 

and was kept closed. 

The building has twelve elevators, ten in the elevator lobby, one freight elevator next to 

D2i and one adjacent to the basement stair opening. Six of the ten main elevators access 

floors 1-28. The remaining four only access floors 1 to 13 (figures 5 and 6). The freight 

elevator extends from the basement to the 29th floor and the elevator adjacent to the 

basement stair opening only serves the basement to the fifth floor. 

The stairwell used for the experiments was located near side A of the building and had a 

half story of steps that led to a landing that transitioned into the actual stair shaft. The 

stair shaft measured 2.44 m (8.0 ft) wide and 5.14 m (16.9 ft) long. There was a 0.1 m 

opening between the stair flights. The stairwell ended at the 29th floor with no access to 

the exterior of the building. The second stairwell in the building provided access to the 

roof and roof hatch but opened only to the exterior of the building at the ground floor 

without room to place a PPV fan (figure 4). 

Floors 2 through 13 were similar with the exception of a few partition walls which had no 

impact on the experiments (figure 5). The two mechanical floors between floor 13 and 
12

floor 14 remained closed and were not used during the experiments. Floors 14 through 

28 were also similar and differed from the lower floors because of the elevators (figure 

6). Floor 29 was not a complete floor and only had a mechanical room and access to the 

lower roof via the roof door (RD) in the stairwell. A ship ladder to the roof hatch (RH) 

provided the only access to the upper roof and was also located in the same stairwell as 

the lower roof door (figure 7). 

 

 

Table 3. Door and hatch dimensions 

Door/Hatch Location Door Dimensions 

(Reference figures 4, 5, 6) Width (m) Height (m) 

D1 1.8 2.1 

D1i 1.5 2.4 

D2 1.1 2.4 

D2i 1.1 2.4 

D3 1.8 2.1 

D3i 1.5 2.4 

S1 0.9 2.4 

S2-S29, S2-S29a 0.9 2.1 

RD 0.9 2.4 

Roof Hatch 0.8 0.9 

 Figure 3. Front (Side A) and left side (Side B) of the building (left photo) and rear (Side C) 

 and right side (Side D) of the building (right photo) 
13

 Figure 5. Floors 2-13 floor plan. 

 

 Figure 4. Ground Floor Plan 

Side C 

Side A 

Side D Side B 

Side C 
14

 Figure 6. Floor 14-28 floor plan. 

 

Figure 7. Floor 29 and roof floor plan. 
15

2.2 Instrumentation 

The measurements taken during the experiments included differential pressure, air 

temperature, carbon monoxide, metrological data and sound levels. A differential 

pressure transducer and thermocouple were located on the door knob of every other floor 

(figure 8). A plastic tube was run under the door to the opposite door knob to reference 

the pressure readings to the floor side (figure 9). The thermocouples were bare-bead, 

type K, with a 0.5 mm (0.02 in) nominal diameter (figure 10). 

Carbon monoxide was measured in the stairwell on floors 1, 14 and 28. Measurements 

were made using a chemical cell monitor with built-in sample pump (figure 11). The 

monitors were also located on the door handle on their respective floors. 

Weather was monitored and recorded during each of the experiments using two portable 

weather stations. Temperature, relative humidity, average wind speed, average wind 

direction and barometric pressure were recorded continuously. One weather station was 

located 9.1 m (30 ft) from the centerline of D2 (figure 12). The second weather station 

was located on the lower roof outside RD (figure 13). 

Sound measurements were taken with an analog sound meter and various locations 

including next to the fan and inside the structure. The meter had an operating range of 

40 dBA to 120 dBA (figure 14). 
16

 Figure 8. Instrumentation layout diagram (P-pressure, T-temperature, CO-carbon monoxide, 

 DL-data logger) 
17

Figure 9. Differential pressure set-up 

Figure 10. Thermocouple location 
18

 

 Figure 11. Carbon monoxide meter 

 Figure 12. Ground weather station 
19

Figure 13. Roof weather station 

 

Figure 14. Sound meter 
20

3.0 Experimental Procedure 

Prior to each of the experiments the setup was configured according to the variables in tables 4-

20. Background measurements were recorded and the fan(s) were started and throttled to full 

speed. The duration of each experiment was three minutes. At the completion of each 

experiment the fan was turned off, readings were allowed to return to ambient and the procedure 

was repeated. 

Table 4. 0.4 m (16 in) fan setback/angle analysis at ground floor stairwell door. 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location Doors Open Vents Open 

 (in) (degrees) (m) 

1 16 90 0.6 D2 D2, S1 None 

2 16 85 0.6 D2 D2, S1 None

3 16 80 0.6 D2 D2, S1 None

4 16 90 1.2 D2 D2, S1 None

5 16 85 1.2 D2 D2, S1 None

6 16 80 1.2 D2 D2, S1 None

7 16 90 1.8 D2 D2, S1 None

8 16 85 1.8 D2 D2, S1 None

9 16 80 1.8 D2 D2, S1 None

10 16 90 2.4 D2 D2, S1 None

11 16 85 2.4 D2 D2, S1 None

12 16 80 2.4 D2 D2, S1 None

13 16 90 3.0 D2 D2, S1 None

14 16 85 3.0 D2 D2, S1 None

15 16 80 3.0 D2 D2, S1 None

16 16 90 3.7 D2 D2, S1 None

17 16 85 3.7 D2 D2, S1 None

18 16 80 3.7 D2 D2, S1 None
21

Table 5. 0.5 m (21 in) fan setback/angle analysis at ground floor stairwell door. 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location Doors Open Vents Open 

 (in) (degrees) (m) 

19 21 90 0.6 D2 D2, S1 None 

20 21 85 0.6 D2 D2, S1 None

21 21 80 0.6 D2 D2, S1 None

22 21 90 1.2 D2 D2, S1 None

23 21 85 1.2 D2 D2, S1 None

24 21 80 1.2 D2 D2, S1 None

25 21 90 1.8 D2 D2, S1 None

26 21 85 1.8 D2 D2, S1 None

27 21 80 1.8 D2 D2, S1 None

28 21 90 2.4 D2 D2, S1 None

29 21 85 2.4 D2 D2, S1 None

30 21 80 2.4 D2 D2, S1 None

31 21 90 3.0 D2 D2, S1 None

32 21 85 3.0 D2 D2, S1 None

33 21 80 3.0 D2 D2, S1 None

34 21 90 3.7 D2 D2, S1 None

35 21 85 3.7 D2 D2, S1 None

36 21 80 3.7 D2 D2, S1 None

Table 6. 0.7 m (27 in) fan setback/angle analysis at ground floor stairwell door. 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location Doors Open Vents Open 

 (in) (degrees) (m) 

37 27 90 0.6 D2 D2, S1 None 

38 27 85 0.6 D2 D2, S1 None

39 27 80 0.6 D2 D2, S1 None

40 27 90 1.2 D2 D2, S1 None

41 27 85 1.2 D2 D2, S1 None

42 27 80 1.2 D2 D2, S1 None

43 27 90 1.8 D2 D2, S1 None

44 27 85 1.8 D2 D2, S1 None

45 27 80 1.8 D2 D2, S1 None

46 27 90 2.4 D2 D2, S1 None

47 27 85 2.4 D2 D2, S1 None

48 27 80 2.4 D2 D2, S1 None

49 27 90 3.0 D2 D2, S1 None

50 27 85 3.0 D2 D2, S1 None

51 27 80 3.0 D2 D2, S1 None

52 27 90 3.7 D2 D2, S1 None

53 27 85 3.7 D2 D2, S1 None

54 27 80 3.7 D2 D2, S1 None
22

Table 7. Best setback/angles at ground floor entrance door 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location Doors Open Vents Open 

 (in) (degrees) (ft) 

56 21 80 1.8 D1 D1, D2i, S1 None 

57 21 85 2.4 D1 D1, D2i, S1 None

58 21 80 1.2 D1 D1, D2i, S1 None

59 27 85 1.2 D1 D1, D2i, S1 None

60 27 80 1.8 D1 D1, D2i, S1 None

61 27 80 1.2 D1 D1, D2i, S1 None

Table 8. Multiple fans at ground floor entrance door (series and parallel configurations) 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location 

Fan 

Orientation Doors Open 

Vents 

Open 

 (in) (degrees) (m) 

62 21 80 1.8, 3.0 D1 series D1, D2i, S1 None 

63 21 80, 85 1.8, 1.8 D1 V D1, D2i, S1 None

64 21 80, 80 1.8, 1.8 D1 V D1, D2i, S1 None

65 21 75, 90 1.8, 1.8, 1.8 D1 V, w, center D1, D2i, S1 None

66 21 80, 80, 80 0.6, 1.8, 3.0 D1 series D1, D2i, S1 None

67 27 85, 85, 85 1.2, 2.4 D1 series D1, D2i, S1 None

68 27 80, 85 1.8, 1.8 D1 V D1, D2i, S1 None 

69 27 80, 80 1.8, 1.8 D1 V D1, D2i, S1 None 

70 27 80, 90 1.8, 1.8, 1.8 D1 V, w, center D1, D2i, S1 None 

71 27, 21 80, 80, 80 1.8, 3.0 D1 V, w, center D1, D2i, S1 None 

Table 9. Multiple fans at stairwell door 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location 

Fan 

Orientation Doors Open 

Vents 

Open 

 (in) (degrees) (m) 

72 21 80 1.8 D2 NA D2, S1 None 

73 21 80, 85 1.8, 3.0 D2 series D2, S1 None

74 21 80, 80, 80 0.6, 1.8, 3.0 D2 series D2, S1 None

75 27 80 1.2 D2 NA D2, S1 None

76 27 80, 80 1.2, 2.4 D2 series D2, S1 None

77 27 80, 80, 80 1.2, 2.4, 3.7 D2 series D2, S1 None

Table 10. Stairwell door(s) open configuration(s) 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location 

Fan 

Orientation Doors Open 

Vents 

Open 

 (in) (degrees) (m) 

78 27 80, 80, 80 1.2, 2.4, 3.7 D2 series D2, S1, S2(2.5") None 

79 27 80, 80, 80 1.2, 2.4, 3.7 D2 series D2, S1, S2 None

80 27 80, 80, 80 1.2, 2.4, 3.7 D2 series D2, S1, S10(2.5") None

81 27 80, 80, 80 1.2, 2.4, 3.7 D2 series D2, S1, S10 None

82 27 80, 80, 80 1.2, 2.4, 3.7 D2 series D2, S1, S20(2.5") None

83 27 80, 80, 80 1.2, 2.4, 3.7 D2 series D2, S1, S20 None

84 27 80, 80, 80 1.2, 2.4, 3.7 D2 series D2, S1, S10, S20 None 
23

Table 11. Fans at multiple ground floor doors 

Experiment 

Fan 

Size 

Fan 

Angle Fan Location 

Fan 

Orientation Doors Open 

Vents 

Open 

 (in) (degrees) 

85 27 All 80 D1, D2, D3 Series, V w/center D1, D2, D3, D2i, S1 None 

86 27 All 80 D1, D3 V w/center D1, D3, D2i, S1 None

Table 12. Fans in the structure 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location Doors Open 

Vents 

Open 

 (in) (degrees) (m) 

87 27 80 1.2 D2 D2, S1 None 

88 27 80, 80 1.2, 1.2 D2 D2, S1, S12 None

89 27 80, 80 1.2, 1.2 D2 D2, S1, S22 None

90 27 80, 80, 80 1.2, 1.2, 1.2 D2 D2, S1, S12, S22 None

91 27 80 1.2 D2 D2, S1, S12 None

Table 13. 46 in trailer mounted fan at ground floor entrances 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location Doors Open Vents Open 

 (degrees) (m) 

92 MVU (1000rpm) 90 10.0 D2 D2, S1 None 

93 MVU (1500rpm) 90 10.0 D2 D2, S1 None

94 MVU (2000rpm) 90 10.0 D2 D2, S1 None

95 MVU (2500rpm) 90 10.0 D2 D2, S1 None

96 MVU (3000rpm) 90 10.0 D2 D2, S1 None

97 MVU (3500rpm) 90 10.0 D2 D2, S1 None

98 MVU (4000rpm) 90 10.0 D2 D2, S1 None 

99 MVU (4500rpm) 90 10.0 D2 D2, S1 None 

100 MVU (4500rpm) 90 10.0 D1 D1, D2i, S1 None 

Table 14. Fans in the structure setback configurations 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location Doors Open Vents Open 

 (in) (degrees) (m) 

101 16 80 in stairwell NA S1 None 

102 16 80 at S12 S12 S1, S12 None

103 16 80 1.2 m back from S12 S12 S1, S12 None

104 16 80 2.4 m back from S12 S12 S1, S12 None

105 27 80 in stairwell NA S1 None

106 27 80 at S12 S12 S1, S12 None

107 27 80 1.2 m back from S12 S12 S1, S12 None 

108 27 80 2.4 m back from S12 S12 S1, S12 None 

109 16, 27 80, 80 1.2 m, 2.4 m back from S12 S12 S1, S12 None 
24

Table 15. Roof door ventilation through 29th floor 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setbac

k 

Fan 

Location Doors Open Vents Open 

 (in) (degrees) (m) 

110 Natural NA NA NA S1, S29, S29a RD 

111 Natural NA NA NA S1, S29, S29a, D2 RD

112 27 80 1.2 D2 S1, S29, S29a, D2 RD

113 27 80 1.8 D2 S1, S29, S29a, D2 RD

114 21 80 1.8 D2 S1, S29, S29a, D2 RD

115 21 80 2.4 D2 S1, S29, S29a, D2 RD

116 16 80 1.2 D2 S1, S29, S29a, D2 RD

117 27 80, 80 1.2, 2.4 D2 S1, S29, S29a, D2 RD

118 21 80, 80 1.2, 2.4 D2 S1, S29, S29a, D2 RD

119 27 80 1.2 S12 S1, S12, S29, S29a, D2 RD

120 27 80 1.2 S12 S1, S12, S29, S29a RD

121 27 80, 80 1.2, 1.2 D2, S12 S1, S12, S29, S29a, D2 RD 

122 27 80, 80, 80 

1.2, 

1.2, 1.2 

D2, S12, 

S22 

S1, S12, S22, S29, 

S29a, D2 

RD 

Table 16. Roof hatch ventilation through 29th floor 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback Fan Location Doors Open 

Vents 

Open 

 (in) (degrees) (m) 

123 27 80, 80, 80 1.2, 1.2, 1.2 D2, S12, S22 S1, S12, S22, S29, 

S29a, D2 

RH

124 27 80, 80 1.2, 1.2 D2, S12 S1, S12, S29, S29a, D2 RH

125 27 80 1.2 D2 S1, S29, S29a, D2 RH

126 NA NA NA NA S1 RH

127 NA NA NA NA S1, D2 RH

Table 17. Roof hatch ventilation through 28th floor 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location Doors Open 

Vents 

Open 

 (in) (degrees) (m) 

128 16 85 1.2 D2 S1, D2, S28, S28a RH 

129 21 80 1.8 D2 S1, D2, S28, S28a RH 

130 27 80 1.2 D2 S1, D2, S28, S28a RH 

131 27 80, 80 1.2, 2.4 D2 S1, D2, S28, S28a RH 

132 27 80, 80, 80 1.2, 2.4, 3.7 D2 S1, D2, S28, S28a RH 

133 21 80, 80 1.2, 2.4 D2 S1, D2, S28, S28a RH 

134 27 80 1.2 D2 S1, S12, D2, S28, S28a RH 

135 27 80 1.2 D2 S1, S12, S28, S28a RH 

136 27 80, 80 1.2, 1.2 D2, S12 S1, S12, D2, S28, S28a RH 
25

Table 18. Ground floor doorway sealed, Fan efficiency 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location Doors Open 

Vents 

Open 

 (in) (degrees) (m) 

137 Blower Door, 21 90 0 D2 S1 NA 

138 Blower Door, 21 90 0 D2 S1 NA 

139 Smoke Curtain, 27 90 0 D2 S1 NA 

Table 19. Other fan types at ground floor stairwell door 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location 

Fan 

Orientation 

Doors 

Open 

Vents 

Open 

 (in) (degrees) (m) 

150 27 80 1.2 D2 NA D2, S1 NA 

151 24 80 1.8 D2 NA D2, S1 NA

152 31 75 2.4 D2 NA D2, S1 NA

153 21 70 2.4 D2 NA D2, S1 NA

154 21 70 1.2 D2 NA D2, S1 NA

155 21 70, 90 1.5, 2.3 D2 V D2, S1 NA

156 21 70, 70 2.4, 2.4 D2 V D2, S1 NA

157 21 70, 70 1.2, 2.4 D2 series D2, S1 NA

158 21 85 1.8 D2 NA D2, S1 NA

159 31, 24 90, 70 2.7,3.0 D2 V D2, S1 NA

Table 20. Hovercraft at ground floor entrance 

Experiment 

Fan 

Size 

Fan 

Angle 

Fan 

Setback 

Fan 

Location 

Doors 

Open 

Vents 

Open 

 (gegrees) (m) 

160 Hovercraft 90 3.7 D3 D3, D2i, S1 NA 

4.0 Results 

4.1 Stairwell Differential Pressure 

 4.1.1 Optimal fan placement at stairwell door (D2) 

Three fan sizes 0.4 m (16 in), 0.5 m (21 in) and 0.7 m (27 in) were used for this series 

(figure 15). Fan setback was varied from 0.6 m (2 ft) to 3.6 m (12 ft) and fan angle 

ranged from 90 degrees to 80 degrees to determine the optimal fan placement. The 

optimal placement is determined by the highest pressures created in the stairwell. 

Background pressures were recorded with D2 open. 

The optimal placement for the 0.4 m (16 in), 5.5 hp fan was 1.2 m (4 ft) and 85 degrees 

(figure 16). A placement of 0.6 m (2 ft) and 85 degrees is the second most optimal 

position. These close distances suggest that there is a large amount of air entrained by 

the air flowing through the shroud of the fan in order to create the seal around the 

doorway by preventing backflow. 
26

The least optimal placement was 3.0 m (10 ft) and 85 degrees, followed by 3.7 m (12 ft) 

and 80 degrees. Another least desired position was 1.2 m (4 ft) and 90 degrees. This 

suggests that the fan tilted to blow straight into the doorway does not create the desired 

airflow to seal the doorway and increase the pressure. 

The 0.4 m (16 in) fan was not able to meet the 28.6 Pa thresholds (Table 1) to prevent 

smoke flow from unsprinklered buildings into the stairwell on any floor. The 12.5 Pa 

threshold for sprinklered buildings was achieved up to the third floor using the optimal 

placement. Many of the non-optimal placements do not meet the sprinklered threshold at 

any floor. 

Increasing the fan size to 0.5 m (21 in) with a 6.5 hp engine resulted in slightly different 

optimal positions. The optimal placement was 1.8 m (6 ft) and 85 degrees (figure 17). 

The second most optimal placement was 1.8 m (6 ft) and 80 degrees. The least optimal 

placement was 3.0 m (10 ft) and 90 degrees. All three angles at 0.6 m (2 ft) and 

90 degrees at 1.8 m (6 ft) produced poor results. These placements also reinforce that 

backflow from the doorway is important to avoid in order to create higher pressures. 

The 0.5 m (21 in) fan was also not able to increase the pressure at any floor to 28.6 Pa. 

However the optimal placement was able to increase the pressure above 12.5 Pa up to the 

ninth floor. Similar to the 0.4 m (16 in) fan many of the non-optimal placements do not 

meet the 12.5 Pa sprinklered threshold (Table 1) at any floor. 

The 0.7 m (27 in) fan with a 9.0 hp engine had an optimal placement of 1.2 m (4 ft) and 

80 degrees (figure 18). The second most optimal placement was 1.8 m (6 ft) and 

80 degrees. The least optimal placements were 3.0 m (10 ft) and 85 degrees, 

3.0 m (10 ft) and 80 degrees, and 0.6 m (2 ft) and 90 degrees. 

Only the optimal placement created pressures above 28.6 Pa for unsprinklered buildings. 

It achieved this pressure only on the first floor. This placement also created pressures 

above 12.5 Pa up to the thirteenth floor. All placements with the 0.7 m (27 in) fan were 

able to reach 12.5 Pa but most were only able to on the lower few floors. 

 

 Figure 15. Fans placed at stairwell doorway, (a) 0.4 m (16 in), (b) 0.5 m (21 in), (c) 0.7 m (27 in) 

(a) (b) (c)
27

0

5

10

15

20

25

30

0 5 10 15 20

Pressure (Pa)

Floor Number

2 ft, 85 degrees

2 ft, 80 degrees

4 ft, 90 degrees

4 ft, 85 degrees

4 ft, 80 degrees

6 ft, 90 degrees

6 ft, 85 degrees

6 ft, 80 degrees

8 ft, 90 degrees

8 ft, 85 degrees

8 ft, 80 degrees

10 ft, 90 degrees

10 ft, 85 degrees

10 ft, 80 degrees

12 ft, 90 degrees

12 ft, 85 degrees

12 ft, 80 degrees

Background

Figure 16. Stairwell pressures created by a 0.4 m (16 in) fan 

0

5

10

15

20

25

30

0 5 10 15 20 25 30

Pressure (Pa)

Floor Number

2 ft, 90 degrees

2 ft, 85 degrees

2 ft, 80 degrees

4 ft, 90 degrees

4 ft, 85 degrees

4 ft, 80 degrees

6 ft, 90 degrees

6 ft, 85 degrees

6 ft, 80 degrees

8 ft, 90 degrees

8 ft, 85 degrees

8 ft, 80 degrees

10 ft, 90 degrees

10 ft, 85 degrees

10 ft, 80 degrees

12 ft, 90 degrees

12 ft, 85 degrees

12 ft, 80 degrees

Background

Figure 17. Stairwell pressures created by a 0.5 m (21 in) fan 
28

0

5

10

15

20

25

30

0 5 10 15 20 25 30 35

Pressure (Pa)

Floor Number

2 ft, 90 degrees

2 ft, 85 degrees

2 ft, 80 degrees

4 ft, 90 degrees

4 ft, 85 degrees

4 ft, 80 degrees

6 ft, 90 degrees

6 ft, 85 degrees

6 ft, 80 degrees

8 ft, 90 degrees

8 ft, 85 degrees

8 ft, 80 degrees

10 ft, 90 degrees

10 ft, 85 degrees

10 ft, 80 degrees

12 ft, 90 degrees

12 ft, 85 degrees

12 ft, 80 degrees

Backgrond

Figure 18. Stairwell pressures created by a 0.7 m (27 in) fan 

 4.1.2 Optimal fan placements at ground floor entrance (D1) 

It is not always possible to place the fan to blow directly into the stairwell doorway. 

Many high-rise buildings only have stairwells that exit onto the ground floor and not 

directly to the outside. Experiments 56-61 examine the pressures created in the stairwell 

by the best placements determined in experiments 1- 54 at a ground floor entrance door 

remote from the stairwell (figure 19). This configuration requires the fan to pressurize 

the ground floor and a portion of the basement due to the open stairwell that connects the 

ground floor to the basement located near side A, adjacent to doorway D1. 

The pressures created by a single fan located at its optimal locations are significantly less 

than those from the fan blowing directly into the stairwell door. At floor 5 the pressures 

created were approximately one-fourth of those obtained with a fan placed at the stairwell 

door (figure 20). Pressures were increased less than 2 Pa at all of the floors. This was 

expected due to the large volume that was added between the fan and the stairwell. 
29

Figure 19. Fan placed at ground level doorway (D1) 

0

5

10

15

20

25

30

0 2 4 6 8 10

Pressure (Pa)

Floor Number

21 in, 6 ft, 80 degrees

21 in, 8 ft, 85 degrees

21 in, 4 ft, 80 degrees

27 in, 4 ft, 85 degrees

27 in, 6 ft, 80 degrees

27 in, 4 ft, 80 degrees

Background

Figure 20. Stairwell pressures from fans blowing into D1 
30

 4.1.3 Multiple fans at ground floor entrance (D1) 

In order to get better performance fire departments often place more than one fan at a 

doorway. Two main questions were addressed with experiments 62 through 71. First, 

does adding a second and third fan double and triple the pressures in the stairwell and 

what is the best way to arrange the fans to achieve the best results? 

Experiments 62 through 66 used 0.5 m (21 in) fans (figure 21). Figure 22 demonstrates 

using additional fans did not cause the pressures to reach the desired magnitudes. All of 

the floors remained below 10 Pa which would not prevent smoke infiltration into the 

stairwell. The orientation of the multiple fans also made a difference in the pressures. 

Placing the fans in a V-shape was more effective than placing them in series. Placing the 

fans in a V-shape with one angled at the top of the door and one at the bottom of the door 

was less effective than angling them both at the center of the door. 

Experiments 67 through 70 used 0.7 m (27 in) fans and experiment 71 used a 

combination of the 0.5 m (21 in) and 0.7 m (27 in) fans. Pressures created by adding 

additional fans were slightly higher than the single fan but did not come close to creating 

adequate pressures, with the exception of floors three through seven when six fans were 

used (figure 23). All of the floors remained below 12.5 Pa, a pressure which would not 

prevent smoke infiltration into the stairwell. The orientation of the multiple fans also 

makes a difference in the pressures. Placing the fans in a V-shape is more effective than 

placing them in series. However with the 0.7 m (27 in) fans, placing the fans in a Vshape with one angled at the top of the door and one at the bottom of the door was more 

effective than angling them both at the center of the door, which is not consistent with the 

0.5 m (21 in) fans. 
31

 

 

 

 

Figure 21. Fans placed at ground floor entrance (D1), a. 2 fans in series, b. 2 fans in V-shape, c. 2 fans in Vshape (top/bottom), d. 3 fans in V-shape w/center, e. 3 fans in series 

 (a) (b) 

 (c) (d) 

 (e) 
32

0

5

10

15

20

25

30

0 5 10 15

Pressure (Pa)

Floor Number

2 - 21 in. fans in series

2 - 21 in. fans in V-shape

2 - 21 in. fans in V-shape (top/bottom)

3 - 21 in. fans in V-shape w/center

3 - 21 in. fans in series

Background

Figure 22. Stairwell pressures from multiple 21 in. fans at D1 

0

5

10

15

20

25

30

0 5 10 15

Pressure (Pa)

Floor Number

2 - 27 in. fans in series

2 - 27 in. fans in V-shape

2 - 27 in. fans in V-shape (top/bottom)

3 - 27 in. fans in V-shape w/ center

3 - 21 in. fans and 3 - 27 in. fans

Background

Figure 23. Stairwell pressures from multiple 27 in. fans at D1 
33

 4.1.4 Multiple fans at stairwell doorway (D2) 

A single fan at the base of the stairwell door (D2) was not able to adequately pressurize 

the stairwell, so, it was necessary to see if multiple fans would be more effective and how 

much more effective that adding one and two additional fans in series. The fans were not 

placed in a V-shape because sufficient space was not available in front of the doorway. 

The first fan was setback 1.2 m (4 ft) and additional fans were placed in 1.2 m (4 ft) 

increments. All fans were set at an 80 degree angle (figure 24). 

A single 0.5 m (21 in) fan created pressures ranging from 26 Pa at the ground floor to 

approximately 8 Pa from the 15th floor to the roof (figure 25). Adding a second 0.5 m 

(21 in) fan in series increased the ground floor pressure to 27 Pa and created a pressure of 

10 Pa from the 15th floor to the roof. Three fans increased the ground floor pressure to 

31 Pa but did not increase the pressure on the floors above the 13th floor. 

A single 0.7 m (27 in) fan created pressures ranging from 24 Pa at the ground floor to 

approximately 8 Pa from the 15th floor to the roof (figure 26). Adding a second 0.7 m 

(27 in) fan in series increased the ground floor pressure to 29 Pa and created a pressure of 

10 Pa from the 15th floor to the roof. Three fans increased the ground floor pressure to 

33 Pa and increased the pressure to 11 Pa on the upper floors. 

 

 Figure 24. Multiple fans in series at stairwell doorway, a. 1.2 m and 2.4 m, b. 1.2 m, 2.4 m and 3.7 m 

(a) (b) 
34

0

5

10

15

20

25

30

0 10 20 30 40

Pressure (Pa)

Floor Number

1.2 m (4 ft)

1.2 m (4 ft) and 2.4 m (8 ft)

1.2 m (4 ft), 2.4 m (8 ft) and 3.7 m (12 ft)

Background

Figure 25. Stairwell pressures from 0.5 m (21 in) fans in series at D2 

0

5

10

15

20

25

30

0 10 20 30 40

Pressure (Pa)

Floor Number

1.2 m (4 ft)

1.2 m (4 ft) and 2.4 m (8 ft)

1.2 m (4 ft), 2.4 m (8 ft) and 3.7 m (12 ft)

Background

Figure 26. Stairwell pressures from 0.7 m (27 in) fans in series at D2 
35

 4.1.5 Open doors in the stairwell 

Open doors in the stairwell are an obvious concern due to the need for the fire department 

to access the floors and for occupants to exit the structure. The added volume of the large 

floors would certainly affect the pressures the fans were able to create in the stairwell. 

Doors were either opened 0.08 m (3 in) to simulate the minimum opening achievable by 

the fire department after stretching a hose line through the doorway or completely open to 

replicate the worst case scenario. The pressures were created with three 0.7 m (27 in) 

fans in series, identical to the configuration in the previous series. 

Opening the doors 0.08 m (3 in) had little impact on the stairwell pressures (figure 27). 

Having the 10th floor slightly open allowed for the 28.6 Pa threshold to be met up to the 

9th floor and the 12.5 Pa threshold to be met in the entire stairwell. With the 2nd floor and 

20th floor slightly opened kept the pressure above 28.6 Pa up to the 5th floor and kept the 

pressure above 12.5 Pa up to the 15th floor. 

Completely opening the doors had a major impact on the stairwell pressures. Having the 

20th floor door open had the least impact on the stairwell pressures while the second floor 

door open had the largest impact. Having the door completely open essentially 

eliminates the effect of the fan in the stairwell on the floors above the open door and 

lowers the pressure of the floors below the floor of the open door as well. With the 20th

floor door open the pressures still maintained the 28.6 Pa threshold up to the 5th floor and 

the 12.5 Pa threshold up to the 13th floor. With the 10th floor door open the pressures 

only maintained the 28.6 Pa threshold on the 1st floor and the 12.5 Pa threshold up to the 

7th floor. With the 2nd floor door open only the 12.5 Pa threshold was met on the 1st floor. 

0

5

10

15

20

25

30

0 10 20 30 40 50

Pressure (Pa)

Floor Number

2nd Floor, 0.08 m (3 in) open

2nd Floor Open

10th Floor, 0.08 m (3 in) Open

10th Floor Open

20th Floor, 0.08 m (3 in) Open

20th Floor Open

10th and 20th Floor Open

Figure 27. Stairwell pressure with doors open 
36

 4.1.6 Multiple fans at multiple ground level doors 

An effort was made to pressurize the stairwell from the ground level by utilizing multiple 

fans in various arrangements. In experiment 85, three 0.7 m (27 in) fans were placed in a 

V-shape at D1, three 0.5 m (21 in) fans were placed in a V-shape at D3 and three 0.4 m 

(16 in) fans were placed in series at D2 (figure 28). In experiment 86, three 0.7 m (27 in) 

fans were placed in a V-shape at D1 and three 0.5 m (21 in) fans were placed in a Vshape at D3, with no fans at D2 assuming that there was no access directly into the 

stairwell. 

Even with nine fans at three different doors the pressure increase was minimal and did 

not even meet the lower threshold pressure at any floor (figure 29). Apparently the larger 

fans at D1 and D3 overpressurized or overwhelmed the smaller fans/open doorway at D2 

and lower pressures resulted (figure 29). Once the smaller fans were removed and 

doorway D2 was closed, the larger fans at D1 and D3 provided higher pressures (figure 

29). Even with the six fans running the lower sprinklered building threshold of 12.5 was 

met up to the ninth floor. Using the same six fans at two doors was more effective than 

using all six at one door as compared to experiment 71 in figure 20. 

 

 Figure 28. Fans placed at multiple doors, a. Fans at D2 and D3, b. Fans at D1 

(a) (b) 
37

0

5

10

15

20

25

30

0 5 10 15 20

Pressure (Pa)

Floor Number

D1, D2, D3

D1, D3

Background

Figure 29. Stairwell pressures with multiple fans at multiple doors 

 4.1.7 Fans located inside the building 

Placing fans at the ground level alone was not effective in meeting the pressure 

requirements necessary to prevent smoke from flowing into the stairwell. This series 

tried to replicate a multiple injection stairwell pressurization system that can be found in 

some buildings. Five different configurations were examined placing 0.7 m (27 in) fans 

on the ground floor, the 12th floor and the 22nd floor. The fans on the upper floors were 

setback and angled just as if they were blowing in from the outside, 1.2 m (4 ft) and 80 

degrees (figure 30). There was no opening to the outside of the building on the 12th or 

22nd floor so little make-up air was available. 

The difference between placing a fan at the ground floor and the 12th floor was 

significant. The fan at the 12th floor created higher pressures from the 5th floor to the top 

floor (figure 31). The pressures from the 13th floor to the roof were more than double 

those from the fan on the ground floor. A single fan on the 12th floor created pressures 

throughout the stairwell that exceeded the 12.5 Pa threshold. Adding a fan at the 1st floor 

elevated the pressures above the 28.6 Pa threshold up to the 15th floor and adding a fan on 

the 22nd floor allowed for the 28.6 Pa threshold to be met on all floors with the exception 

of floors 21 and 27. The lower pressures on 27 appear to be consistent with decrease in 

pressure as one moves away from the fan. 
38

Figure 30. Fan positioned in the building 

0

5

10

15

20

25

30

0 10 20 30 40

Pressure (Pa)

Floor Number

Fan at floor 1

Fan at floor 1 and 12

Fan at floor 1 and 22

Fan at floor 12

Fan at floor 1, 12 and 22

Figure 31. Stairwell pressures with fans inside the building 
39

 4.1.8 1.2 m (46 in) trailer mounted fan at ground floor entrance 

The smaller, compartment size fans were not effective from the ground so a larger trailer 

mounted fan was utilized for a series of experiments. The 1.2 m (46 in) fan was 

positioned 10.0 m (32.8 ft) from the stairwell doorway and was not angled (figure 32). 

The engine speed was increased by 500 rpm increments, up to 4500 rpm, and steady state 

pressures were recorded for each level. Experiments were stopped at 4500 rpm, close to 

the maximum output of the fan, due to concerns for glass breakage. 

At 3500 rpm the fan was able to pressurize the entire stairwell to the 12.5 Pa sprinklered 

building minimum pressure (figure 33). When increased to 4500 rpm the stairwell 

pressures were above the 28.6 Pa unsprinklered pressure threshold. The highest steady 

state pressure, 103 Pa, was recorded on the 1st floor, with the fan set to 4500 rpm. 

Pressures of this magnitude border on the upper threshold which should not be exceeded 

if occupants are to readily open the doors to exit the building. 

Figure 32. Trailer mounted fan at stairwell door. 
40

0

5

10

15

20

25

30

0 20 40 60 80 100 120

Pressure (Pa)

Floor Number

1000 rpm

1500 rpm

2000 rpm

2500 rpm

3000 rpm

3500 rpm

4000 rpm

4500 rpm

Figure 33. Stairwell pressures made by the 1.2 m (46 in) fan at the stairwell door. 

 4.1.9 Further analysis of fans located inside the building 

Since elevated pressure results were successfully achieved in the previous series of 

experiments with fans located inside the building, additional configurations were 

analyzed. This series focused on the setback of the fan in the building at the 12th floor. 

Fans were placed in the stairwell with the stairwell door shut, at the stairwell door, 

setback 1.2 m (4 ft), setback 2.4 m (8 ft) and two fans in series at the stairwell doorway 

(figure 34). 

The fans placed in the stairwell slightly increased the stairwell pressures above the 12th

floor and decreased the pressures below the fan level (figure 35). This configuration was 

not effective and could actually draw flows downward in the building. The 0.4 m (16 in) 

fan was not able to increase the pressure on any floor above 10 Pa which does not meet 

either desirable pressure threshold. The 1.2 m (4 ft) setback with an angle of 80 degrees 

was more effective than the 2.4 m (8 ft) setback with an angle of 80 degrees and the fan 

positioned in the doorway. 

The 0.7 m (27 in) fan was able to raise the pressure on all floors above the 12.5 Pa 

threshold with three different setbacks, in the doorway, 1.2 m (4 ft) back from the door 

and 2.4 m (8 ft) back from the door. The optimal setback was 1.2 m and 80 degrees. 

This placement created pressures above 19 Pa on every floor, with a maximum pressure 

of 28 Pa recorded on floor 13. This setback even outperformed both fans in series. 
41

 

 

 

 

Figure 34. Fans locations in the stairwell 

(a) (b) (c) 

(d) 
42

0

5

10

15

20

25

30

0 10 20 30 40

Pressure (Pa)

Floor Number

16 in. fan in stairwell

16 in. fan at stairwell door

16 in. fan 1.2 m (4 ft) setback

16 in. fan 2.4 m (8 ft) setback

27 in. fan in stairwell

27 in. fan at stairwell door

27 in. fan 1.2 m (4 ft) setback

27 in. fan 2.4 m (8 ft) setback

16 in. and 27 in. fan in series

Background

Figure 35. Stairwell pressures created with fans at the 12th floor. 

4.1.10 Fans at ground level and in the building with the bulkhead 

door open 

A common tactic in venting a high-rise building is opening the bulkhead door at the top 

of the stairwell, if there is one. In this building the bulkhead door was in the second 

stairwell, therefore both doors to the 29th floor were opened so the flow would travel 

through the 29th floor into the other stairwell and out of the bulkhead door. This tactic 

often allows for smoke to escape and create more tenable conditions in the stairwell both 

for civilians attempting to exit and fire fighters. This series of experiments examined the 

pressure decrease in the stairwell when the 29th floor and the bulkhead door in the other 

stairwell were opened. 

After completing this series of experiments it was noticed that there was an exhaust fan 

on the 29th floor that forced air to the outside. This is common on mechanical floors but 

changes the meaning of the pressures recorded for this series only. Pressures in the top of 

the stairwell were lower than expected because of the negative pressure created by the 

exhaust fan. The pressures can be treated as a worst case scenario as opposed to ideal 

which will be examined in a later series which uses the 28th floor as opposed to the 29th

floor to eliminate the exhaust fan from the path to the vent locations (bulkhead door and 

roof hatch). 
43

Background data was recorded to examine the pressures in the building with just the 

bulkhead door open and then with the stairwell door open. When the stairwell door was 

opened it induced pressures in the lower portion of the stairwell as high as 11 Pa at the 

ground floor. The pressure declined to approximately 0 Pa at floor 19 (figure 36). 

Three different configurations were analyzed, 0.5 m (21 in) fans at ground level, 0.7 m 

(27 in) fans at ground level and 0.7 m (27 in) fans on the 12th floor. The pressures on the 

upper floor drop significantly when the 29th floor and the bulkhead doors were opened. 

The pressures above the 20th floor dropped from 9 Pa to 0 Pa with the 29th floor and 

bulkhead doors open. Two 0.5 m (21 in) fans were able to create pressures exceeding the 

28.6 Pa threshold up to the 3rd floor and 12.5 Pa threshold up to the 11th floor. 

A 0.7 m (27 in) fan located at the ground level created pressures of approximately 9 Pa 

above the 15th floor with all the stairwell doors closed (figure 37). Those pressures 

dropped to 0 Pa when the 29th floor and the bulkhead doors were opened. When two fans 

were used the 12.5 Pa thereshold was exceeded up to the 11th floor, even with the vents 

opened. When the fan was moved to the 12th floor the doors opened at the top and the 

bottom of the stairwell were analyzed (figure 38). With the 29th floor and bulkhead doors 

open, the pressures dropped as much as 21 Pa to 0 Pa at the 27th floor. The ground floor 

door open in addition to the 29th floor and bulkhead doors had little impact on the 

stairwell pressures. 

0

5

10

15

20

25

30

0 10 20 30 40

Pressure (Pa)

Floor Number

BH open, Stairwell door closed

BH open, Stairwell door open

21 in. fan, 1.8 m (6 ft) and 80 degrees

21 in. fan, 2.4 m (8 ft) and 85 degrees

2 - 21 in. fans, 1.2 m (4 ft) and 2.4 m (8 ft), both 80 degrees

21 in. fan, 1.8 m (6 ft) and 80 degrees, BH closed

Figure 36. Stairwell pressures created by 0.5 m (21 in) fans with the 29th floor and bulkhead door open. 
44

0

5

10

15

20

25

30

0 10 20 30 40 50

Pressure (Pa)

Floor Number

BH open, Stairwell door closed

BH open, Stairwell door open

27 in. fan, 1.2 m (4 ft) and 80 degrees

27 in. fan, 1.8 m (6 ft) and 80 degrees

2 - 27 in. fans, 1.2 m (4 ft) and 2.4 m (8 ft), both 80 degrees

27 in. fan, 1.2 m (4 ft) and 80 degrees, BH closed

Figure 37. Stairwell pressures created by 0.7 m (27 in) fans at the ground level with the 29th floor and 

bulkhead door open. 
45

0

5

10

15

20

25

30

0 10 20 30 40

Pressure (Pa)

Floor Number

BH open, Stairwell door closed

BH open,Stairwell door open

27 in. fan on 12th floor, Stairwell

door closed

27 in. fan on 12th floor, Stairwell

door open

27 in. fan on 12th floor, Stairwell

door closed, BH closed

Figure 38. Stairwell pressures created by 0.7 m (27 in) fans on the 12th floor with the 29th floor and 

bulkhead door open. 

 4.1.11 Fans at ground level and in the building with the roof hatch 

open 

Adjacent to the bulkhead door on the 29th floor was a ship-style ladder that led to a roof 

hatch. The roof hatch was the highest point of the building and the most remote 

ventilation location from the ground level entrances. In this series the exhaust fan on the 

29th floor was removed from the flow path by opening both stairwell doors to the 28th

floor and flowing through the 28th floor to the roof hatch. Configurations were run with 

single fans at ground level, multiple fans at ground level, and fans inside the building. 

The series of experiments began with pressures recorded with just the roof hatch open. 

This did not provide any pressure above ambient (figure 39). The stairwell door was 

opened and pressures below the 15th floor increased. The 1st floor pressure increased to 

7 Pa, decreasing down to 1 Pa at the 15th floor. The 0.4 m (16 in) fan was only able to 

increase pressures approximately 3 Pa and never exceeded 10 Pa. The 0.5 m (21 in) fan 

increased pressures on the first floor to 25 Pa and met the 12.5 Pa threshold to the 9th

floor. Increasing the fan size to 0.7 m (27 in) increased the 1st floor pressure to 32 Pa. 

The 12.5 Pa threshold was exceeded up to the 11th floor. Without an exhaust fan in the 

flow path pressures were slightly increased up to the 25th floor whereas in the previous 

series the pressures were not increased above the 21st floor with single fans located at 

ground level. 
46

Fans were added in series to try to increase the pressures in the stairwell. When a second 

0.5 m (21 in) fan was added in series an increase of approximately 2 Pa was achieved 

throughout the stairwell (figure 40). This provided little benefit and increased the 12.5 Pa 

threshold from the 9th floor to the 10th floor. A second 0.7 m (27 in) fan in series 

increased pressures in the lower floors from approximately 4 to 6 Pa. The 12.5 Pa 

threshold was raised from the 11th to the 13th floor. Adding a third 0.7 m (27 in) fan in 

series provided very little benefit and raised stairwell pressures less than 2 Pa at all floors. 

A single 0.7 m (27 in) fan was placed on the 12th floor positioned as previously described 

and the door at the base of the stairwell was placed in the open and closed position. 

Having the door closed created higher pressures below the 12th floor (figure 41). Closing 

the door increased the average 1st floor stairwell pressure from 10 Pa to 17 Pa. Above the 

12th floor the position of the ground floor stairwell door was irrelevant. When a second 

0.7 m (27 in) fan was added at ground level the pressures were increased close to the 

28.6 Pa threshold up to the 13th floor. In all three configurations the 12.5 Pa threshold 

was reached up to the 13th floor. 

0

5

10

15

20

25

30

0 10 20 30 40 50

Pressure (Pa)

Floor Number

RH open, Stairwell door closed

RH open, Stairwell door open

16 in., 1.2 m (4 ft) and 85 degrees

21 in., 1.8 m (6 ft) and 80 degrees

27 in., 1.28 m (4 ft) and 80 degrees

Figure 39. Stairwell pressures created by a single fan with the 28th floor and roof hatch open. 
47

0

5

10

15

20

25

30

0 10 20 30 40 50

Pressure (Pa)

Floor Number

RH open, Stairwell door closed

RH open, Stairwell door open

2 - 21 in, 1.2 m (4ft) and 2.4 m (8 ft)

2 - 27 in, 1.2 m (4ft) and 2.4 m (8 ft)

3 - 27 in, 1.2 m (4ft) and 2.4 m (8 ft), 3.6 m (12 ft)

Figure 40. Stairwell pressures created by multiple fans with the 28th floor and roof hatch open. 

0

5

10

15

20

25

30

0 10 20 30 40 50

Pressure (Pa)

Floor Number

RH open, Stairwell door closed

RH open, Stairwell door open

27 in., 12th floor, RH open, Stairwell door open

27 in., 12th floor, RH open, Stairwell door closed

2 - 27 in., Ground floor and 12th floor

Figure 41. Stairwell pressures created by fans in the building with the 28th floor and roof hatch open. 
48

 4.1.12 Ground level doorway sealed / Fan efficiency 

Positive pressure ventilation fans setback from a doorway seal the doorway with a cone of 

air to increase the pressure. The distance the fan is from the doorway, or setback, can 

impact how effective a PPV “seals” the doorway. A fixed stairwell pressurization system 

usually has a fan, or multiple fans, that are connected directly to the stairwell with no 

setback and in turn should be 100 % efficient at using its flow to increase the pressure in 

the stairwell. In an attempt to recreate a similar situation, the ground floor doorway was 

sealed with an air infiltration door test frame and a 0.5 m (21 in) fan was placed in the 

hole to flow into the building with no air escaping because of a setback distance. 

As compared to the optimal setback configuration determined in a previous series, sealing 

the door created higher pressure throughout the stairwell. Pressures increased as much as 

8 Pa to 2 Pa at the ground level and at the 27th floor respectively (figure 42). Assuming 

the fan flowing with the sealed door is completely efficient, the fan setback at its optimal 

distance and angle is 80 % efficient. While sealing the door is more efficient it eliminates 

the ability for fire fighters to enter the stairwell from that doorway and for occupants to 

exit via that doorway. 

0

5

10

15

20

25

30

0 10 20 30 40

Pressure (Pa)

Floor Number

21 in. fan with sealed doorway

21 in. fan, 1.8 m (6 ft) and 85 degrees

Background

Figure 42. Stairwell pressures created by a 0.5 m (21 in) fan with the doorway sealed and with the fan 

setback 
49

 4.1.13 Other types of fans at the ground level stairwell door 

PPV manufacturers and representatives were invited to take part in the experiments. Two 

additional manufacturers brought fans. The fans ranged in size from 0.5 m (21 in) to 

0.8 m (31 in) with engines ranging in size from 5.5 hp to 12.0 hp. The fans were 

positioned at the ground level stairwell doorway and the stairwell was pressurized with all 

vents closed. The fans were initially setup at the doorway by the manufacturer’s 

representative. Additional configurations such as side by side and series were done for 

comparison (figure 43). 

As expected, the larger the fan the higher the pressures created in the stairwell (figure 44). 

The 0.8 m (31 in) fan created pressures as high as 41 Pa at the ground floor. The 0.6 m 

(24 in) fan peaked at 30 Pa on the ground floor. The 0.5 m (21 in) fan reached 23 Pa and 

the Toledo truck fan (has been in service for over 10 years on a Toledo Fire Department 

truck company) only raised the first floor stairwell pressure to 8 Pa. The 0.8 m (31 in) fan 

was able to exceed the 12.5 Pa threshold in the entire stairwell while the smaller fans 

were effective for less than half of the stairwell height. 

A few different configurations were experimented with the 0.5 m (21 in) fans, 1.2 m 

setback, 2.4 m setback, side by side (same angle, V), offset (top and bottom, R) and series 

(S). The 2.4 m setback with a 70 degree angle created higher pressures than the 1.2 m 

setback with a 70 degree angle. The offset fans with 70 degree and 90 degree angles 

created higher pressures than the side by side with the same angle which created higher 

pressures than the fans in series. Adding the 0.6 m (24 in) fan to the 0.8 m (31 in) raised 

pressures 8 Pa on the ground floor and approximately 1 Pa above the 17th floor. The old 

fan that was taken off of the Toledo ladder truck did not perform well, not coming close 

to achieving the 12.5 Pa threshold anywhere in the stairwell. 

Different fans are constructed different ways and cannot always be compared directly due 

to different sized motors, shroud type and size and fan angle adjustments. However, 

common trends exist. Placing the fans next to each other as opposed to in series is more 

effective. It is possible to have a single fan achieve 12.5 Pa in the entire stairwell but that 

fan maybe large and may not fit in a truck compartment. PPV fans have improved greatly 

in the last 10 years and older fans should be checked for performance and replaced if 

necessary to allow for increased effectiveness. Different fan manufacturers have different 

optimal setbacks and angles due to many differences, such as shrouds and fan blades. 

 
50

 

 

 

Figure 43. Other types of fans and configurations. (a) 2 – 21 in. fans side by side (b) 2 – 21 in. fans in series 

(c) 24 in. and 31 in. fans side by side (d) 21 in. Toledo truck fan 

(a) (b) 

(c) (d) 
51

0

5

10

15

20

25

30

0 10 20 30 40 50 60

Pressure (Pa)

Floor Number

24 in, 9.5 hp (R)

31 in, 12.0 hp (R)

21 in, 5.5 hp (R)

21 in, 5.5 hp (4 ft)

2 - 21 in, 5.5 hp (R)

2 - 21 in, 5.5 hp (V)

2 - 21 in, 5.5 hp (S)

21 in, 5.5 hp (Toledo Truck)

31 in, 12.0 hp and 24 in, 9.5 hp (R)

Figure 44. Pressures created by other manufacturer’s fans in various configurations 

 4.1.14 Fans and a hovercraft at ground floor entrances (D1 and D3) 

Many fire departments have been resourceful when they had to remove smoke from a 

large structure and have occasionally used a hovercraft or airboat. Oftentimes, a 

hovercraft is much more accessible than a large trailer mounted fan. A hovercraft was 

used in the experiments for comparison against a trailer mounted fan. The hovercraft was 

setback 3.7 m (12 ft) from the ground entrance door (D3) and was run at full throttle 

(figure 45). 

The hovercraft was approximately as effective as a previous experiment where six fans 

were utilized (3 - 0.7 m (27 in) fans at D1 and 3 – 0.5 m (21 in) fans at D3) (figure 46). 

Pressures peaked at 15 Pa on the 5th floor and decreased to an average of 8 Pa in the upper 

half of the stairwell. The 1.2 m (46 in) trailer mounted fan positioned at D1 created much 

higher pressures, exceeding the 12.5 Pa threshold in the entire stairwell. 
52

Figure 45. Hovercraft positioned at ground floor entrance (D3) 

0

5

10

15

20

25

30

0 10 20 30

Pressure (Pa)

Floor Number

Hovercraft at D3

MVU at D1

3 Fans at D1 and D3

Figure 46. Stairwell pressures created by fans and hovercraft positioned at D1 and D3 
53

4.2 Stairwell Temperature 

Temperature was recorded on every other floor with bare-bead, type K thermocouples, 

with a 0.5 mm (0.02 in) nominal diameter. Thermocouples were located next to each of 

the differential pressure transducers. There was no temperature control in the building; 

therefore the stairwell temperatures were very similar to the outside temperatures. The 

temperature in the lower floors ranged between 19 oC (66 oF) in the morning hours to 

23 oC (73 oF) in the afternoon. The temperature in the upper floors of the stairwell 

remained almost constant at about 25 oC (77 oF) to 26 oC (79 oF) independent of the day 

the experiments were done or of the time of day (figure 47). This small variation in 

temperature between the inside temperatures and the outside temperatures suggests the 

impact of stack effect in the stairwell was minimal 

0

5

10

15

20

25

30

0 10 20 30

Temperature (oC)

Floor Number

Experiment 9

Experiment 27

Experiment 49

Experiment 63

Experiment 85

Experiment 95

Experiment 131

Experiment 154

Figure 47. Stairwell temperatures 
54

4.3 Weather 

Weather was monitored and recorded during each of the experiments using two portable 

weather stations. Temperature, relative humidity, average wind speed, average wind 

direction and barometric pressure were recorded continuously. One weather station was 

located 9.1 m (30 ft) from the centerline of D2 on ground level. The second weather 

station was located on the lower roof outside RD. Each day started at time zero and 

readings were captured every 30 seconds. Technical difficulties with the wireless link 

between the weather station and the data logger resulted in some data loss, but the trends 

of the data were captured. 

The average air temperature was recorded over the course of the four days of experiments 

at the ground and the roof. The average temperatures remained fairly constant during all 

of the experiments. Temperatures ranged between 16 oC (61 oF) and 25 oC (77 oF) 

(figure 48). The morning temperatures were cooler than the afternoon temperatures but 

there was never an increase of more than 5 o

C (9 oF) during the entire day. 

Wind speed has the potential to greatly impact the effectiveness of PPV. Wind blowing 

against an exhaust vent could decrease the effectiveness of PPV. Wind blowing into an 

inlet could increase the air flow or increase pressurization of a building. The average 

wind speed mostly remained below 2 m/s (4.5 mph) (figure 49). The wind had little 

impact on the experimental results. If there was wind there were no gusts that would give 

one experiment an advantage or disadvantage from another experiment in the same 

series. The average wind direction was also examined to determine if the wind was into 

or out of one of the inlets or vents. The wind mainly impacted the building on side B and 

C, between zero and 140 degrees from north (figure 50). The north arrow can be 

referenced to the inlets and outlets in figure 4 and figure 7. Therefore the wind had no 

direct impact on the inlets on side A and little impact on the roof door on side C. A wind 

impacting the opposite side of the building from the inlets has the potential to lower the 

pressure on the leeward side of the building. This phenomenon did not play a role in 

these experiments due to the low magnitude of the wind speed. The stairwells were also 

interior to the building which lessened the impact of any wind. 

The relative humidity and barometric pressure did not show any variations that may have 

affected the results. The relative humidity ranged between 20 % and 70 % (figure 51). 

The relative humidity decreased as it became later in the day. The barometric pressure on 

the roof was between 98 kPa and 99 kPa and between 99 kPa and 100 kPa at ground level 

(figure 52). 
55

0

10

20

30

40

50

0 5000 10000 15000 20000

Experiment 2-54 Ground

Experiment 56-100 Ground

Experiment 56-100 Roof

Experiment 101-149 Ground

Experiment 101-149 Roof

Experiment 150-160 Ground

Experiment 150-160 Roof

Average Temperature (oC)

Time (s)

Figure 48. Average temperatures. 

0

1

2

3

4

5

0 5000 10000 15000 20000

Experiment 2-54 Ground

Experiment 56-100 Ground

Experiment 56-100 Roof

Experiment 101-149 Ground

Experiment 101-149 Roof

Experiment 150-160 Ground

Experiment 150-160 Roof

Average Wind Speed (m/s)

Time (s)

Figure 49. Average wind speed. 
56

0

60

120

180

240

300

360

0 5000 10000 15000 20000

Experiment 2-54 Ground

Experiment 56-100 Ground

Experiment 56-100 Roof

Experiment 101-149 Ground

Experiment 101-149 Roof

Experiment 150-160 Ground

Experiment 150-160 Roof

Average Wind Direction (degrees from north)

Time (s)

Figure 50. Average wind direction. 

0

20

40

60

80

100

0 5000 10000 15000 20000

Experiment 2-54 Ground

Experiment 56-100 Ground

Experiment 56-100 Roof

Experiment 101-149 Ground

Experiment 101-149 Roof

Experiment 150-160 Ground

Experiment 150-160 Roof

Relative Humidity (%)

Time (s)

Figure 51. Relative humidity. 
57

96

97

98

99

100

101

102

0 5000 10000 15000 20000

Experiment 2-54 Ground

Experiment56-100 Ground

Experiment 56-100 Roof

Experiment 101-149 Ground

Experiment 101-149 Roof

Experiment 150-160 Ground

Experiment 150-160 Roof

Barometric Pressure (kPa)

Time (s)

Figure 52. Barometric pressure. 

4.4 Carbon Monoxide 

One of the main toxic gases in combustion is carbon monoxide (CO). When examining PPV 

and preventing smoke infiltration there are two types of combustion that are important, the fire 

creating the smoke and the internal combustion of the fan motor. Both sources of CO must be 

monitored to maintain a safe environment for victims as well as fire fighters. 

A fire has the potential to produce a very large amount of CO. This amount could be on the 

order of 50,000 ppm in an under-ventilated fire [15]. Tenability limits for incapacitation and 

death for a 5 minute exposure are 6000 ppm (0.6 %) to 8000 ppm (0.8 %) and 12,000 ppm 

(1.2 %) to 16,000 ppm (1.6 %) respectively. CO is the major toxic gas in approximately 67 % of 

fatalities in structure fires [15]. Using PPV fans to keep the CO produced by the fire along with 

the other harmful combustion products out of the stairwells greatly increases the chances of safe 

evacuation. 

The internal combustion fan motors also produce CO. While the levels are much lower than the 

fire they have to be analyzed. CO meters were placed at the bottom, middle and top of the 

stairwell to analyze this level. The National Institute for Occupational Safety and Health 

(NIOSH) has established a recommended exposure limit for CO of 35 ppm (0.0035 %) as an 
58

8-hour time weighted average (TWA) and 200 ppm (0.02 %) as a ceiling exposure [16]. A 

reading of 1200 ppm (0.12 %) is considered immediately dangerous to life and health. The 

National Research Council (NRC) also defines emergency exposure guidance levels of, 

1500 ppm ( 0.15 %) for 10 minutes, 800 ppm (0.08 %) for 30 minutes, 400 ppm (0.04 %) for 

60 minutes and 50 ppm (0.005 %) for 24 hours [17]. 

CO levels for the four days of experiments are graphed in figures 53 through 56. The single fan 

at the ground floor stairwell created readings as high as 110 ppm (0.011 %) at the 1st floor with a 

0.7 m (27 in) fan set back 0.6 m (2 ft) from the doorway. The reading decreased to 30 ppm 

(0.003 %) when the fan was run at 3.7 m (12 ft). The optimal fan placements for all three sizes 

of fans created CO readings of 50 ppm (0.005 %) to 80 ppm (0.008 %). The experiments were 

run one right after another with no venting of any openings between experiments. There was a 

break between fan sizes to allow for the CO readings to return to ambient. 

Any number of fans placed at the ground level did not exceed readings of 100 ppm (0.01 %). 

Nine fans blowing into the building from three different ground level doorways did not raise the 

CO reading above 100 ppm (0.01 %). The 1.2 m (46 in) trailer mounted fan did not exceed 

50 ppm (0.005 %) at any level in the stairwell. 

The fire service becomes very concerned with the idea of taking gasoline powered fans into a 

structure. This was done multiple times to see the actual CO levels created. A single 0.7 m 

(27 in) fan set back from the 12th floor door did not exceed 100 ppm (0.01 %). With a 0.7 m (27 

in) fan at the ground level in addition to the one on the 12th floor the CO readings peaked at 

130 ppm (0.013 %). Adding another 0.7 m (27 in) fan to the 22nd floor increased the peak CO 

reading on the 14th floor to 140 ppm (0.014 %) but also increased the 28th floor CO level to 

110 ppm (0.011 %). The only two experiments that caused the CO levels to exceed the NIOSH 

ceiling exposure value of 200 ppm (0.02 %) were when a fan was placed in the stairwell and the 

stairwell doors were closed. In these experiments the 0.4 m (16 in) fan created a peak CO 

reading of 210 ppm (0.021 %) in the stairwell at the 14th floor and the 0.7 m (27 in) fan had a 

peak reading of 360 ppm (0.036 %) in the same configuration. 

Ultimately the CO produced by the PPV fans was at least one order of magnitude less than that 

created by a fire. As long as the PPV fans were not placed in the stairwell with the door shut, the 

NIOSH ceiling exposure was not exceeded and the TWA would not be exceeded for a long 

period of time. If CO readings are less than 50 ppm (0.005 %), it is not likely that a gasoline 

powered PPV fan would be effective in ventilating the area. In this case alternatives such as 

electric PPV fans or natural ventilation should be considered. 
59

0

20

40

60

80

100

120

0 5000 10000 15000 20000

Floor 1

Floor 14

Floor 28

Carbon Monoxide (ppm)

Time (s)

Exp 2-18 Exp 19-36 Exp 37-54

Meters Off for 

Data Download

Figure 53. Carbon monoxide levels for experiments 2 through 54. 
60

0

20

40

60

80

100

120

140

0 5000 10000 15000 20000 25000 30000

Floor 1

Floor 14

Floor 28

Carbon Monoxide (ppm)

Time (s)

Exp 56-71 Exp 72-86 Exp 87-91 Exp 92-100

Meters Off for 

Data Download

Figure 54. Carbon monoxide levels for experiments 56 through 100. 
61

0

50

100

150

200

250

300

350

400

0 5000 10000 15000 20000 25000

Floor 1

Floor 14

Floor 28

Carbon Monoxide (ppm)

Time (s)

Exp 101-109

Exp 134-136

Exp 126-133

Exp 110-125 Exp 137-139

Meters Off for 

Data Download

Figure 55. Carbon monoxide levels for experiments 101 through 139. 
62

0

10

20

30

40

50

60

70

0 2000 4000 6000 8000 10000

Floor 1

Floor 14

Floor 28

Carbon Monoxide (ppm)

Time (s)

Exp 150-159

Exp 160

Figure 56. Carbon monoxide levels for experiments 150 through 160. 

4.5 Sound Levels 

Another concern with the use of PPV fans is the noise they create. Fans placed at the base of a 

stairwell can increase the ambient noise in the stairwell and may adversely affect the 

communications of the fire crews. Fans placed at lobby doors have the potential to affect 

command officers that may set up command posts in high-rise structures. 

Noise levels were monitored in certain locations throughout the experimental series to estimate 

the level of impact to the fire crews and command officers. Ambient noise measurements were 

60 to 65 dB. This value rose to 80 dB when traffic went past the building. Measurements next 

to the compartment size fans were approximately 100 dB to 110 dB depending on the size of the 
63

fan. The noise value measured 3.0 m (10 ft) from the fans decreased to 90 to 100 dB. Table 21 

has a number of common noise levels for comparison. 

A 0.7 m (27 in) fan was placed 3.7 m (12 ft) from the stairwell doorway. Readings next to the 

fan were 105 dB with the fan at full throttle, directly inside the doorway with the door open were 

104 dB. In the lobby with the door shut the readings decreased to 77 dB but increased to 95 dB 

when the door connecting the stairwell and lobby was opened. On the second floor landing, the 

reading decreased to 80 dB. Similar readings were obtained with a 0.5 m (21 in) fan placed at 

the same setback distance. 

Table 21. Relative Noise Levels 

Source of Sound/Noise Sound Pressure 

Level (dB) 

Threshold of hearing 0 

Quiet bedroom at night 30 

Conversational speech 60 

Curbside of busy roadway 80 

Heavy Truck 90 

Jackhammer 100 

Chainsaw 110 

Threshold of pain 130 

Instant perforation of eardrum 160 

5.0 Uncertainty 

There are different components of uncertainty in the length, differential pressure, gas 

temperature, metrological, and carbon monoxide data reported here. Uncertainties are grouped 

into two categories according to the method used to estimate them. Type A uncertainties are 

those which are evaluated by statistical methods, and Type B are those which are evaluated by 

other means [18]. Type B analysis of systematic uncertainties involves estimating the upper (+ 

a) and lower (- a) limits for the quantity in question such that the probability that the value would 

be in the interval (± a) is essentially 100 %. After estimating uncertainties by either Type A or B 

analysis, the uncertainties are combined in quadrature to yield the combined standard 

uncertainty. Multiplying the combined standard uncertainty by a coverage factor of two results 

in the expanded uncertainty which corresponds to a 95 % confidence interval (2σ). 

Components of uncertainty are tabulated in Table 22. Some of these components, such as the 

zero and calibration elements, are derived from instrument specifications. Other components, 

such as differential pressure, include past experience with the instruments. 

Each length measurement was taken carefully. However due to some issues, such as 

obstructions and unlevel terrain there was a total expanded uncertainty of ± 6 % associated with 

the length measurements. 
64

Differential pressure reading uncertainty components are derived from pressure transducer 

instrument specifications. The transducers were factory calibrated and the zero and span of each 

was checked in the laboratory prior to the experiments. 

Gas temperature measurements were taken in a very low range of less than 30 oC. There were no 

temperature fluctuations of large magnitude and no radiative effects. Calibration data was 

obtained from the thermocouple manufacturer and the measurements appeared very repeatable. 

Weather, carbon monoxide and sound measurement uncertainty was referenced to each of their 

published user’s manuals. Weather and CO instruments have calibration certificates that are 

traceable to NIST standards. The carbon monoxide meters were factory calibrated prior to the 

experiments. The sound meter had a self-calibration setting. 

Table 22. Uncertainty 

Component 

Standard 

Uncertainty 

Combined 

Standard 

Uncertainty 

Total 

Expanded 

Uncertainty 

Length Measurements 

 Instrumentation 

 Locations 

 Fan Location 

 Building Dimensions 

 Repeatability1

 Random1

± 1 % 

± 1 % 

± 1 % 

± 2 % 

± 2 % 

± 3 % ± 6 % 

Differential Pressure 

 Calibration [19] 

 Accuracy [19] 

 Repeatability 1

 Random 1

± 2 % 

± 1 % 

± 3 % 

± 3 % 

± 5 % ± 10 % 

Gas Temperature 

 Calibration[20] 

 Repeatability1

 

 Random1

± 0.75 % 

± 1 % 

± 1 % 

± 1 % ± 2 % 

Weather Measurements 

 Temperature[21] 

 Relative Humidity 

 Average Wind Speed 

 Wind Direction 

 Barometric Pressure 

 Repeatability1

 Random1

± 2 % 

± 2 % 

± 1 % 

± 1 % 

± 0.003 % 

± 1 % 

± 1 % 

± 3 % ± 6 % 
65

Carbon Monoxide 

Measurements 

 Calibration[22] 

 Accuracy[22] 

 Repeatability1

 Random1

± 1 % 

± 0.002 % 

± 2 % 

± 2 % 

± 2 % ± 4 % 

Sound Measurements 

 Calibration[23] 

 Accuracy[23] 

 Repeatability1

 Random1

± 1 % 

± 3 % 

± 2 % 

± 2 % 

± 4 % ± 8 % 

Notes: 1. Random and repeatability evaluated as Type A, other components as Type B. 

6.0 Discussion 

For this limited series of experiments, the fan setback distance and angle needed to be optimized 

in order to maximize the impact of the fan. The fans used in these experiments had optimal 

configurations of 1.2 m (4 ft) and 85 degrees for the 0.4 m (16 in) fan, 1.8 m (6 ft) and 85 

degrees for the 0.5 m (21 in) fan, and 1.2 m (4 ft) and 80 degrees for the 0.7 m (27 in fan). The 

setback distances suggest that PPV fans rely on the air that is entrained around the shroud from 

air being pulled through the shroud to achieve the cone of air to seal the doorway. The fans 

positioned right in front of the doorway, which had limited air entrainment, were not able to raise 

the pressures in the stairwell as well as the fans set back from the doorway. 

This set of full-scale experiments indicates that when possible the PPV fan should be placed at 

the stairwell doorway and not at another ground floor entrance. Adding the volume of the first 

floor makes any number of fans at the ground floor entrances ineffective, especially above the 

10th floor. This may not hold for buildings with smaller lobbies or with first floors that can be 

sectioned off to limit the volume, but typically high-rise buildings have large open lobbies. 

During these ambient temperature experiments, placing PPV fans in series was less effective 

than placing the fans in a V-shape. When the fans were in a V-shape it did not seem to make a 

large difference if the fans were at the same angle or if one was angled at the top and the other at 

the bottom of the doorway. If building geometry prevents the fans from being placed in a Vshape, adding a second fan in series only increases the pressure by approximately 25 % and a 

third fan an additional 10 %. 

Similar to fixed smoke control systems, opening stairwell doors has a large impact on stairwell 

pressures. Opening a stairwell door reduces the pressure on floors above the open door to 

approximately ambient, eliminating the desired impact of the PPV fan. A significant increase in 

pressure could be achieved by closing the doorway to the width of a hoseline. If the fire crew 

closes the doorway on their hoseline instead of keeping the door completely open, the amount of 

smoke that infiltrates into the stairwell will be greatly reduced. This will be of significant benefit 

to the people exiting through this stairwell and fire crews operating above the fire floor. 
66

Placing fans in the building was the only way to effectively pressurize the stairwell. In a 30-

story stairwell a 0.7 m (27 in) fan placed at the ground floor and one 0.7 m (27 in) fan set back 

from the 12th floor stairwell doorway greatly increased the pressure in the entire stairwell. There 

was no make-up air provided to the fans set back in the building. This is not necessary as the fan 

recirculates the same air to the stairwell doorway maintaining the pressure on a continuous basis. 

The fans positioned in the building were more effective when configured using the same optimal 

setback and angle described previously for fans at the ground floor stairwell doorway. Placing 

the fans in the doorway was ineffective because there was no cone of air to seal the doorway. 

Also, moving the fans back to 2.4 m (8 ft) was less effective. Fans should not be placed in the 

stairwell; this resulted in lower pressure differentials and generated significant amounts of CO in 

the stairwell. 

Examining the effects of the fan on the 12th floor and the fan on the 22nd floor it may be most 

effective to place a 0.7 m (27 in) fan at the stairwell doorway 2 floors below the fire to get the 

desired pressures and reduce the impact of doors opening on any of the floors. This 

configuration also allows for ventilation in addition to pressurization. The smoke that has 

already infiltrated the stairwell could be vented out of the top of the stairwell while the localized 

pressure will prevent any additional smoke from entering the stairwell. The data suggest that this 

will work on sprinklered buildings even with the top and bottom of the stairwell open and the 

pressures are borderline to work on an unsprinklered building based on the threshold pressures 

required. 

When venting the top of the stairwell and pressurizing the stairwell, a smaller vent such as a roof 

hatch should be considered rather than a bulkhead or roof door in order to maximize the 

potential pressure differential. A roof hatch is usually large enough to vent sufficient smoke 

while small enough to increase the pressure in the stairwell. 

Fixed stairwell pressurization systems usually have at least one fan that is built into a wall or the 

top of the stairwell. The pressure loss due to the fire department fan being set back as opposed to 

sealed in the doorway yielded an 80 % efficiency based on the comparison of pressure 

differences. This setback allows access and egress from the fan inlet doorway which is essential 

for most fire department operations. The 20 % loss has little impact on the overall ability of the 

fans to pressurize the stairwell. 

The large trailer-mounted fan was able to pressurize the stairwell to the NFPA 92A 

unsprinklered threshold in the entire stairwell when utilized on the stairwell doorway. It was 

also able to pressurize the stairwell to the unsprinklered threshold at the other ground floor 

entrance when it had to pressurize the entire first floor and basement in addition to the stairwell. 

Attention needs to be given to the maximum allowable pressure with these large fans in order to 

ensure that the pressure does not prevent the opening of doors into the stairwell. This value is 

specified in national codes such as NFPA 101 or in local codes and is a function of stairwell door 

size, handle location and door closer force. This value is often approximately 80 Pa to100 Pa 

which the large fans are capable of creating in the lower portions of the stairwell. 
67

The hovercraft created stairwell pressures that were below the standards minimum. The 

hovercraft’s performance could be replicated by multiple compartment sized fans. If multiple 

compartment sized fans are not available the hovercraft may be a good choice to vent a large 

volume but not to pressurize a stairwell to a desired pressure differential. 

There are multiple fan manufacturers and each of them has differences whether it is blade type, 

shroud size, engine power rating, etc. Not all PPV fans behave the same and it is important to 

utilize them optimally to get the desired performance. These results provide guidance to the 

important variables but may not be relevant to all fan types. As technology improves so will the 

ability of the fans to move air. The fans used in these experiments represent the best current 

technology available and the size and power rating of the fans may not be representative of older 

fans that may currently be on fire apparatus. 

Temperature can be an important variable when pressurizing a stairwell. In these experiments 

the temperature in the stairwell was very similar to the outside temperature which minimized the 

impact of stack effect. In cases where the outside temperature is lower than the stairwell 

pressure there tends to be an upward movement of air in the stairwell. Air in the building is 

often warmer and therefore less dense than outside air causing it to rise in the stairwell. This 

causes smoke to accumulate on the upper floors and reinforces the need to ventilate along with 

pressurization. 

The CO produced by the PPV fans was at least one order of magnitude less than that created by a 

fire. As long as the PPV fans were not placed in the stairwell with the door shut, the NIOSH 

ceiling exposure was not exceeded. However, CO readings less than 50 ppm are unlikely with a 

gasoline powered PPV fan. Electric PPV fans or natural ventilation should be considered if CO 

readings less than 50 ppm are desired. 

The noise levels created by the fans reached as high as 110 dB next to the fan at full throttle. 

This is comparable to a chainsaw and can have an impact on communications on the fire ground. 

Attempting a conversation or radio transmission near the PPV fan was difficult both for the 

sender and receiver. Attention should be given to the location of the command post and potential 

for PPV fan usage locations. 

7.0 Future Research 

The results of these experiments provide guidance for fan placement to be effective against 

smoke flow due to pressure differences. The performance metric was provided by NFPA 92A 

but needs to be tested in live fire experiments. The experiments should focus on realistic fire 

conditions in high-rise structures and integrate the use of the fans into fire department standard 

operating procedures to determine if conditions can in fact be improved for both the occupants 

exiting the building and for firefighters performing fire ground operations. 

Additionally a standard test needs to be developed and followed to provide the fire service with a 

set of performance metrics such as flow capacity so that they may make educated decisions on 

which fans work for their needs. Currently the Air Movement and Control Association 
68

International, Inc. (AMCA) has a standard entitled “Laboratory Method of Testing Positive 

Pressure Ventilators for Rating.” This standard is meant to establish a uniform method for 

laboratory testing of PPV fans in order to determine performance in terms of airflow rate, 

pressure, air density, and speed of rotation for rating or guarantee purposes. 

Further testing should be done to determine the relevance of the current AMCA standard to fire 

fighting operations. If the standard were mandatory for all manufacturers the fire service would 

have a means to determine the effectiveness of a particular fan for a certain application. 

Currently the fire service has attributes such as fan size and motor power but that is not directly 

applicable to particular applications. It would be valuable to be able to label or certify a fan to be 

capable of generating a specified capacity of air allowing the fire fighter to determine if that flow 

capacity meets their needs for an incident. Formulas, like those for fire fighting flow rates, 

could be developed for positive pressure ventilation operations. The formula would incorporate 

the height of the building or the volume of the building to aid fan selection. Such a standard 

would require additional data gathered collaboratively with all affected parties. 

8.0 Conclusions 

Positive pressure ventilation fans utilized correctly can increase the effectiveness of fire fighters 

and survivability of occupants in high-rise buildings. In a high-rise building it is possible to 

increase the pressure of a stairwell to prevent the infiltration of smoke if fire crews configure the 

fans properly. When configured properly PPV fans can meet or exceed previously established 

performance metrics for fixed smoke control systems. Proper configuration requires the user to 

consider a range of variables including, fan size, set back, and angle, fan position inside or 

outside of the building, and number and alignment of multiple fans. 

The data collected during this limited set of full-scale experiments in a 30-story office building 

demonstrated that in order to maximize the capability of PPV fans the following guidelines 

should be followed: 

• Regardless of size, portable PPV fans should be placed 1.2 m (4 ft) to 1.8 m (6ft) set back 

from the doorway and angled back at least 5 degrees. This maximizes the flow through 

the fan shroud and air entrainment around the fan shroud as it reaches the doorway. 

• Placing fans in a V-shape is more effective than placing them in series. 

• When attempting to pressurize a tall stairwell, portable fans at the base of the stairwell or 

at a ground floor entrance alone will not be effective. 

• Placing portable fans inside the building below the fire floor is a way to generate pressure 

differentials that exceed the NFPA 92A minimum requirements. For example, if the fire 

is on the 20th floor, placing at least one fan at the base of the stairwell and at least one 

near the 18th floor blowing air into the stairwell could meet the NFPA 92A minimum 

requirements. 

• Placing a large trailer mounted type fan at the base of the stairwell is another means of 

generating pressure differentials that exceed the NFPA 92A minimum requirements. 

• Fans used inside the building should be set back and angled just as if it were positioned at 

an outside doorway. 
69

The experiments also document that PPV fans can be loud which may have an impact on fire 

ground and command post communications. Gasoline powered fans generate carbon 

monoxide but the magnitude has to be compared to that of the hazard created by the fire in 

the building. Overall, when properly setup and correctly operated, positive pressure 

ventilation is a tool which the fire service can use to improve the safety and effectiveness of 

fire ground operations. 

 
70

9.0 References 

1. NFPA 101, Life Safety Code. National Fire Protection Association, Quincy, MA., 2006. 

 

2. Grant, Casey,C., Triangle Fire Stirs Outrage and Reform, NFPA Journal, May/June 1993, 

pp73-82. 

3. Hall Jr., John. High-rise Building Fires. NFPA, Quincy, MA. August 2005. 

4. Traumatic Firefighter Fatalities in High-rise Office Buildings in the United States 1977-

Present, NFPA Database Search. National Fire Protection Association, Quincy, MA. January 

2007. 

5. Isner, Michael, S., Fire Investigation Report: High-Rise Office Building Fire, Alexis Nihon 

Plaza, Montreal, Canada, October 26, 1986. National Fire Protection Association, Quincy, 

MA. 

6. Nelson, Harold, E., An Engineering View of the Fire of May 4, 1988 in the First Interstate 

Bank Building, Los Angeles, California. NISTIR 89-4061. National Institute of Standards 

and Technology, Gaithersburg, MD. March 1989. 

7. Klem, Thomas J., Fire Investigation Report: One Meridian Plaza, Philadelphia, PA, February 

23, 1991. National Fire Protection Association, Quincy, MA. 

8. Madrzykowski, D., and Walton, W.D., Cook County Administration Building Fire, 69 West 

Washington, Chicago, Illinois, October 17, 2003: Heat Release Rate Experiments and FDS 

Simulations, NIST Special Publication, SP-1021. National Institute of Standards and 

Technology, Gaithersburg, MD. July 2004. 

9. NIOSH ALERT:Preventing Injuries and Deaths of Fire Fighters. National Institute for 

Occupational Safety and Health (NIOSH), Morgantown, WV. September 1994. 

10. Three Fire Fighters Die in a 10-Story High-Rise Apartment Building – New York. Fire 

Fighter Fatality Investigation Report F99-01. National Institute for Occupational Safety and 

Health (NIOSH), Morgantown, WV. August 1999. 

11. High-Rise Apartment Fire Claims the Life of One Career Fire Fighter and Injures Another 

Career Fire Fighter – Texas. Fire Fatality Investigation Report F2001-33. National Institute 

for Occupational Safety and Health (NIOSH), Morgantown, WV. October 2002. 

12. DeCicco, P.R., Cresci, R.J., and Correale, W. H., “Fire Tests, Analysis and Evaluation of 

Stair Pressurization and Exhaust in High-Rise Office Buildings”, New York: Polytechnic 

Institute of Brooklyn, 1972. 
71

13. NFPA 92A. Standard for Smoke-Control Systems Utilizing Barriers and Pressure 

Differences. 2006 Edition. 

14. Tempest Technology Corporation, http://www.tempest-edge.com, January 2003. 

15. Purser, David. “Toxicity Assessment of Combustion Products.” The SFPE Handbook of 

Fire Protection Engineering, National Fire Protection Association, Quincy, MA, Third 

Edition (2002). 

16. NIOSH [1992]. Recommendations for occupational safety and health: Compendium of 

policy documents and statements. Cincinnati, OH: U.S. Department of Health and Human 

Services, Public Health Service, Centers for Disease Control, National Institute for 

Occupational Safety and Health. DHHS (NIOSH) Publication No. 92-100. 

17. NRC [1987]. Emergency and continuous exposure guidance levels for selected airborne 

contaminants. Vol. 7. Ammonia, hydrogen chloride, lithium bromide, and toluene. 

Washington, DC: National Academy Press, Committee on Toxicology, Board on Toxicology 

and Environmental Health Hazards, Commission on Life Sciences, National Research 

Council, pp. 17-38. 

18. Taylor, B.N., and Kuyatt, C.E., Guidelines for Evaluating and Expressing the Uncertainty of 

NIST Measurement Results. NIST Technical Note 1297. National Institute of Standards and 

Technology, Gaithersburg, MD. January 1993. 

19. Setra Systems, Inc., Installation Guide, Setra Systems Model 264 Differential 

Pressure Transducer. Boxborough, MA., 1999. 

20. Omega Engineering Inc., The Temperature Handbook, Vol. MM, pages Z-39-40, 

Stamford, CT., 2004. 

21. Weatherpak – 2000 User’s Manual. Coastal Environmental Systems. December 9, 1997. 

22. Q-RAE Multi-gas Monitor. Operational and Maintenance Manual. Document No.:027-

4001-000, Rev. B. May 2005. 

23. Sound Meter 84005 Instruction Manual. Sper Scientific Ltd. May 11, 2005. 
72

10.0 Acknowledgments 

The authors would like to thank Roy McLane and Ryan Travers of the Building and Fire 

Research Laboratory for their invaluable support during the preparation and implementation of 

the experimental series. The authors would also like to thank Chief John Coleman and the 

Toledo Fire Department for inviting NIST to participate and the endless support they provided. 

Special thanks to representatives from the Fire Department of New York and the Chicago Fire 

Department for their guidance and assistance during the experiments. Tempest, Euramco and 

SuperVac supplied resources and provided technical support in order to make the experiments 

possible. Finally, the authors express gratitude to the Department of Homeland Security, Mr. 

Randall Griffin and Mrs. Meredith Lawler for their sponsorship and support of this important 

and ongoing research.