###### Abstract
[9]); (3) large scale outdoor compartment fire experiments determining the difference between timber and steel clad ISD fire behaviour ([PERSON] et al. [10]), fire spread ([PERSON] et al. [11]), and critical separation distance; (4) full scale laboratory experiments to understand the fire dynamics and the effect of different boundaries ([PERSON] et al. [12]) and test current theories for temperature, flame shape, and flashover conditions ([PERSON] et al. [13]); (5) modelling the results of these experiments to determine controlled experiments required to validate the Fire Dynamics Simulator (FDS) ISD models [14] and the utility of FDS in capturing fire dynamics in ISDs ([PERSON] [9; 15]); (6) wind tunnel simulations to understand the effects of the wind on the fire dynamics ([PERSON] et al. [16]); and (7) fire risk mapping using remote sensing and GIS techniques ([PERSON] et al. [17]) for fire spread modelling ([PERSON] et al. [18]) and determining critical separation distance ([PERSON] et al. [19]). Figure 1: Large scale experiment performed via the IRIS-Fire project [2] in 2018 emphasizing the size of the external plume from vertical openings (doors and window) and leakage at joins of walls and roofs. In all the previous experimental and modelling work highlighted above, the fires have followed the trend of ventilation-controlled fires. In more detail, ventilation-controlled fires are highly affected by both the size and location of the openings [20]; therefore, to further understand the fire dynamics in relation to the ventilation in ISDs, numerical parametric studies were conducted. [PERSON] et al. [21] studied the effect of the ventilation location (the dwelling's window) in relation to the fire dynamics and the external plume behaviour. It was found that the heat flux from the vertical openings (door and window) could vary by up to 60% depending on the relative position of the window from the door and presented the theoretical optimal location of the window relative to the door on each wall. [PERSON] et al. [22] then studied numerically, using FDS, the effect of adding horizontal openings (collapsible roofs) to the design of the ISDs, where the idea is simply to cut out parts of the steel-clad roofs of the ISDs and add a thin flammable material with low ignition temperature (e.g., polycarbonate) to collapse, or burn, due to the contact with the hot gas layer before flashover. This will create vents for the gas layer's hot smoke to escape. The presence of a horizontal openings will allow combustion products to leave the compartment while cool air enters through the vertical openings located at the floor level. This is expected to significantly increase the ventilation to the fire [20] as illustrated in Figures 2-4, lower heat fluxes to the combustibles (Q\({}_{\text{RI}}\)), increase times to flashover (T), and shorten projected flame lengths from the vertical openings (_Xi_). The study [22] proved the potential validity of the method for reducing the risk of spread at vertical dwelling openings; therefore, an experimental study was needed to further investigate the idea and validate the FDS code for these conditions. Figure 3: Illustration of pre-flashover (**a**) and post-flashover (**b**) conditions inside a dwelling with vertical openings only. Figure 2: Illustration of fire development in compartments. Horizontal openings have been studied a few times in fire safety research. [PERSON] et al. [23] developed a simplified mathematical model to predict the vertical temperature profiles in enclosures without vertical openings. This model was performed on two types of compartments: one without any openings and another with only horizontal (root vents). The model was then validated against experimental work on a large scale (3.0 \(\times\) 3.0 \(\times\) 1.95 m) compartment with a pool fire and thermocouple (TC) tree to measure the temperature profile, where the vent was placed in one of the corners. The model, however, is inadequate for use in the current study due to the lack of the vertical openings as a factor.