"We carried out further tests using 'Chiltern International Fire' testing facilities in High Wycombe and have scientific evidence that proves using PPV offensively causes no further damage to a casualty located between the seat of the fire and the exhaust vent, than that which has  already occurred prior to the commencement of firefighting........."

                                   Tyne & Wear Metropolitan Fire Brigade

Based upon such evidence the UK Generic Risk Assessment (GRA 3.6) advises -

'The use of forced ventilation is likely to increase the intensity of the fire, and if incorrectly used it may increase the risk of injury to any persons within the building. Recent studies have indicated that the likelihood of increasing the risk to the occupants of the building are far outweighed by the benefits of, rapid improvements in the internal conditions and by more effective fire attack'.

However, it is perhaps more likely that an overly cautious approach remains prudent where occupants remain trapped in fires, especially in locations sited between the fire and the PPV outlet point. The introduction of a forced airflow from a PPV ventilator may worsen conditions at the casualty location in several ways and one might even pose the question - should PPV be used offensively in situations where occupant location is unkown?

Mostyn Bullock (Chiltern Fire) writes - 'it is not my intention to give the impression that I would support the idea that heat flux at the casualty location is always reduced by PPV.  Indeed our data (regarding Test 3) indicated that the reverse was true in that heat flux levels reached 33KW/m2n at the casualty location as a result of the offensive use of PPV accelerating a flashover of the fire. I would support a view that offensive PPV needs very careful deployment, especially where occupants may be trapped downstream of the fire'.........

Lets imagine a situation where an occupant has made it to an upstairs bedroom window  and opened the window in an attempt to escape but collapsed due to smoke conditions in the room (a viable scenario). If a PPV airflow was to force an amount of  super-heated combustible fire gases from the exhaust outlet (window) and they were to ignite on mixing with the outside air, conditions inside the compartment would dramatically worsen. The heat-flux at the casualty location would most likely rise; the oxygen entering and being made available to the occupant would be severely restricted; and the smoke layer in the room would plunge to the floor, where the casualty is located.

Another situation might arise where a trapped occupant has made it  near to the open window and is calling for help just as the PPV airflow is directed into the structure. The casualty will most likely be forced to jump from the upper floor than suffer the consequences of a sudden and dramatic rise in temperature as super-heated gases are driven in the direction of (and exit) the outlet.

A recent scientific research report from Finland, into the use of PPV, recognised the potential for both fuel-controlled and under-ventilated fires to intensify as the forced airflow reaches the fire compartment.

It remains far from 'proven' that offensive PPV applications are unlikely to worsen a trapped occupant's situation under the wide range of variables that are possible, particularly where the person remains between the fire and the exhaust vent. More research in this area is needed before such an approach can be relied upon.

Basement Fire Kills Firefighter - REPORT HERE

NIOSH SUMMARY