Reserach Activity | 東京理科大学研究推進機構総合研究院火災科学研究所

Area of Fire Dynamics

In the Fire Dynamics Research Area, fundamental studies are conducted to elucidate the phenomena related to fire, combustion and explosion. In this issue, results of research on toxicity gas test and the mechanism of smoldering to flaming transition are reported.

In order to replace the toxicity testing of combustion product gases of building interior materials in Japan and to investigate alternative methods for the use of laboratory animals, a Fourier Transmission Infrared Spectrophotometer (FT-IR) was installed in the current gas toxicity test apparatus and the behavior stopping time of mice obtained from the gas toxicity test was compared with that obtained from the FT-IR. The Fractional Effective Dose (FED) was calculated from data obtained by the FT-IR. Using the FED, we analyzed the results focusing on CO₂, which is classified as a simple asphyxiant gas as well as a chemical asphyxiant gas among the toxic gases. The results correlated well with the behavioral time of mice when the CO₂ concentration was taken into account in the study using FED as a method of toxicity evaluation in gas toxicity testing equipment.

The transition from smoldering combustion, which is a low-temperature, slow reaction, to faster, high-temperature flaming combustion can occur under certain conditions. This transition phenomenon is often observed in cigarette-related fires and wildfires, triggering a rapid escalation of fire damage. In 2024, a mathematical model was developed to predict the critical conditions for this transition (Fig. 2). The model reveals that the smoldering mode dominates under low oxygen concentrations, while a coexistence region for both smoldering and flaming combustion emerges as oxygen levels increase. Beyond a critical oxygen threshold, flaming combustion becomes the sole reaction mode. The model also predicts the influence of other external factors, such as airflow velocity, on transition conditions.

**Fig.1.** Relationship between FED and time of mouse action cessation.

**Fig.2.** Combustion-mode map predicted by the newly developed model.

Area of Evacuation and Human Behavior

“Security measures for evacuation safety”

Access control devices such as security gates are increasingly being installed in buildings. There is concern that access control devices for crime prevention purposes may hinder evacuation and firefighting activities. In this study, measures to ensure safety in evacuation were examined through a survey of security such as access restrictions on evacuation routes. Experiments were conducted on subjects to operate emergency locks, and data was collected and analyzed, such as the time it took to unlock four types of emergency locks and open the door, and the force required to unlock them. The time required to open varied greatly depending on the type of emergency lock. It ranged from 6.3 seconds to 27.6 seconds on average. In particular, it took nearly 60 seconds to unlock Type-B and Type-C, with six people and three people giving up, respectively. The order of ease of operation was Type-D > A > B ≒ C overall. Except for Type-D, it is difficult to understand how to unlock the lock at first glance, and it can be said that there are issues with operating it in an emergency. The order of ease of operation is roughly as expected, but there is little correlation between ease of operation and the force required to unlock.

**Fig. 3.** Four types of emergency locks

Area of Fire Resistance for Structural Members and Materials for Disaster Prevention

“Experimental study on fire behavior near ceilings surrounded by wooden hanging walls”

This study aimed to collect technical knowledge on fire behavior near ceilings with exposed wooden beams and hanging walls, and conducted experiments assuming a ceiling surrounded by wooden hanging walls (Photo 2). In the experiment, a ceiling with plan dimensions of 0.9m x 0.9m and 0.9m x 1.8m was surrounded by wooden hanging walls, and the effects of the depth of the hanging walls and the fire source conditions on the incident heat and combustion properties to the hanging walls were confirmed under conditions where the entire hanging walls were heated uniformly.

As a result, in a space surrounded by wooden hanging walls, when all four hanging walls were closed, there was a lack of oxygen near the ceiling surface, and although the smoke layer temperature reached 500-600°C, the index of flashover occurrence, there was no rapid fire spread, and flaming combustion was only near the fire source. In addition, if the fire source conditions and the depth of the hanging wall are the same, the smaller the planar size of the ceiling surrounded by the hanging wall, the more likely it is that heat will be trapped, and the more likely it is that the pyrolysis of the wooden hanging wall will be accelerated.

Area of Firefighting, Fire Prevention, and Industry Fires

Research is conducted from the perspectives of “advancing firefighting activities through the use of science and technology” and “protecting against fires caused by chemicals and industrial activities.”

Concerning research on health management and effective training methods for the prevention of occupational accidents among firefighters, we are collaborating with fire departments to continuously conduct studies in which physiological indicators are measured during training sessions with firefighters wearing their actual gear. These studies aim to develop management methods to ensure operational safety and to devise effective training programs. Additionally, we have conducted research analyzing the temporal changes in firefighters’ heat acclimatization training on-site to reduce the risk of heatstroke during summer firefighting operations. Other research topics include the utilization of drone technology in fire and disaster prevention, and the evaluation of fire extinguishing agents with consideration for environmental impact.

We have also investigated energy and environmental issues related to industrial development and fire hazards from the perspective of chemical substances. For example, studies have been conducted on hazardous substances in forestry and wildfires, fires involving renewable, recycled materials and biomass power plants,

and the fire risks of inorganic compounds such as nuclear power plant waste.

In addition to the above, we have also conducted experiments on the thermal runaway of lithium-ion batteries (Fig.6) and on the dispersion of leaked gases (Fig.7)