Annals
of the M.B.C. - vol. 1° - n° 1 - September 1987
FOREST FIRES AND THE PREVENTION OF BURNS: STUDY AND DEVELOPMENT OF A
PROTECTIVE OUTFIT
Magliacani G.
Traumatological Centre of Turin - Plastic Surgery
Division - Burn Treatment Centre
SUMMARY. Forest fires
are not a rare event in Mediterranean countries and they present some peculiar
characteristics which affect the types of risk involved, of which the main one is of
course burning.The statistically most frequent accidents are lue to sudden flares of flame
or by sudden change in the direction of the fire front where fire-fighting teams are at
work. In such cases t ic temperature of the heat source reaches maximum levels that may be
supposed to be in the region of 500'C; the time of exposure of the fi.-e-fighter is
generally 20-30 sec.
We have accordingly designed protective clothing to avert the risk of burns or to limit
their effect, taking into account the environmental and climatic conditions in which fires
break out ard their characteristic physical features. This type of clothing has the
following specifications:
- easy to wear and comfortable even when used for long periods
- protects all the body, and in particular those parts most at risk - face, hands,
perineum etc.
- protection time sufficient to allow wearer to pass through fire front at the estimated
temperature
- poor accumulator of heat
- allows wearer to feel gradual rise of temperature so that he is aware of imminent
danger.
Among the causes of burns to
be considered with the utmost attention on account of the incidence and severity of the
damages involved, we should certainly include forest fires, a field in which specialist
physicians, in collaboration with other technicians, can make significant contributions.
Forest fires, in fact, are a frequent occurrence in the Mediterranean countries, mostly,
but not limited to, in the summer season, developing in the bush or amid the trees and
undergrowth.
Mediterranean bush fires are characterised by a flame front about 1,5 to 2 metre thick,
2,5 metre high, spreading at a speed of approx. 20/30 cm/sec, and producing an amount of
heat per Kg of fuel fully burnt of 3,800 Kcal.
In the case of forest fires preying on tall-trunks, such as Coniferae, the thickness of
th,- front is greater (5 to 10 metres), its height is that of tt. c trees involved, but in
actual practise combustion above 2,5 m does not lead to a significant temperature increase
at ground level. The fires spreads at a lower pace, the energy produced is reduced and the
temperature is not as high as in bush fires.
The hazards to be faced by operators engaged in fire quenching operations include, first
of all, burns, and secondly traumas which may be produced by the fall of bodies no longer
propped up by the vegetation, especially on.slopes, as well as cuts, grazes and other
types of wound.
Burns may be due to the fall of incandescent particles, contact with flames suddenly
flaring up, an abrupt eh ange in the direction of the flame front produced by wind gusts,
a common ~:)ccurrence especially along the sea-coast.
Particularly severe are the bums caused by unsuitable clothes or protective outfits which
transfer heat by conduction to the operator's skin they are in contact with while the
operator is being overtaken by the fire front.
The exchange of heat through the skin, in fact, takes place much faster, the temperature
being the same, when heat is applied by conduction rather than by convection or radiation.
The damages produced by direct contact with the flame are compounded by exposure to the
radiant heat that precedes and follows the front.
However, the temperature peak, highest at the centre where it reaches a maximum estimated
value of approx. 50WC, generally only lasts a few seconds, by the radiant heat moving with
the front, and the time of exposure must be raised by an adjustment coefficient to 30
seconds.
Therefore, the fire front should be viewed as a line moving on and giving rise to an
increase in temperature that begins in the form of radiant heat, then continues to
increase until it suddenly reaches and maintains for about 10 seconds peak values at
centre,. followed by a gradual decrease with further generation of radiant heat at the
rear of the front, this process as a whole lasting approx. 30 seconds.
The foregoing information was used to study the characteristics of a protective suit which
might suitably ward off the hazards firemen are exposed to when fighting a forest fire.
In order to be effective, the protective equipment should entail a difference between the
time it takes the inner wall of the outfit (when exposed to the heat source) to rearch the
burn producing temperature (T 1) and the time required to reach the same temperature when
no shielding is provided (T).
Having set the protecticri time TP = Tl - T, the higher the TP value, the gre~ ter the
protective capacity afforded.
When the values T 1 and T coincide the outfit has no protective value in that it makes no
difference whatsoever.
When TP is negative, tte outfit is dangerous and its utilization should be prevented.
For our purposes a sufficient degree of protection is deemend to be provided i -the time
difference as a whole exceeds 30 seconds at 300'C will have a TP of only 6 seconds at
500'C.
As we have seen the front has different temperatures over its thickness, hence at all
times the TP value must be higher than the time it takes the flame front, with its
different temperature values, to overtake a stationary operator, in order to ensure a
safety margin is always provided and guarantee effective protection.
To be regarded as safe, an outfit must afford longer protection times in the regions
classified as . risk- areas, that is, in the body regions of major aesthetic-functional
importance, whose impairment entails difficulties in the administration of treatment and
the risk of invalidating effects, such as the face, neck, hands, feet, the perineum and
the joints.
An outfit must be comfortable, so that it can be worn throughout the operation. Hence it
must not be too heavy, and it must be designed to permit adequate perspiration, sufficient
freedorn of movement to the operator's limbs, sensitivity of the hands, these being the
indispensable prerequisites for sustained use.
Summer and winter models must be provided, both in compliance with the above-mentioned
characteristics.
Moreover, the protective garment must be easy to take off so that it is possible to
quickly remove from the operator any residual heat accumulated by the fabric when in
contact with the flame.
Protection must be exte ided to the entire body, paying the greatest attention to the
"risk" regions, where protective capacity is expected to be highest.
The manufacturing system and the type of materials used must be such that they will
guarantee full protection over the entire tirrie of exposure to the fire front and in the
event of a sudden flare up.
Hence, the materials used must be fireproofed, which does not amount to no i inflammable
materials, but ones burning with a latency time before heat is transferred to the skin,
with no residual combustion and dripping.
Fabric suitability must ah.o be ensured by adequate strength against the typical stresses
of forest areas which might cause ripping arid tear.
Further characteristics include the lack of pockets or loose parts that might be caught in
the vegetation and damage the garment, as well as the elimination of any projecting part
which might easily catch fire.
The metal parts, if present, must never come in contact with the flame and with the skin,
since this might in turn give origin to burns.
Double seams must be provided, with the outer seam protecting the inner one, so as to
prevent the flame from producing an opening in the fabric and exposing a portion of the
body to the heat.
Finally, we believe that a protective device conceived in this manner must enable the
operator to perceive the gradual increase in temperature and become aware of impending
danger so that he can move away from the heat source.
A further warranty of safety for the users is the stability of these characteristics over
time.
The outfit produced in keeping with the foregoing provisions (PROMEPACK - PROMETEO) is
composed of helmet, cap, hood, overalls, shirt and gloves. It allows for three different
protection factors, according to the different functional importance and vulnerability of
the body regions.
With the aim of assessing the garment's effectiveness laboratory tests were performed by
exposing the suit's walls to heat flows of 200, 300, 400 and 500'C - that is the
temperature values of the fire front - and measuring the heat increments directly on the
inner wall of the protective outfit.
During these tests, comparative measurements were also performed on clothes manufatured by
traditional methods (outfits A and B).
The results obtained are listed in a table, stating the TP in seconds for the specimens
examined.
|
Factor 1 |
Factor 2 |
Factor 3 |
Outfit A |
Outfit B |
200
300
400
500 |
104
30
10
6 |
151
47
25
12 |
180
122
113
49 |
10
2.5
2
1 |
13
3
3
1,5 |
|
TABLE
1 |
|
Since a suit's heat insulation value cannot be regarded as absolute, that
is, sufficiently high to ensure full protection at all times and under any circumstances,
the operators should be informed of the protection limits of the outfit.
A protective device perfectly suited to cope with a specific situation may lose its
effectiveness when the thresholds determined at the design stage are exceded.
This entails the need of adequate training programmes with detailed instructions on the
suit's proper utilization, i.e. learning under which conditions it will provide maximum
protection and being able to perceive approaching danger, so as to avoid the phase in
which protection becomes precarious.
In conclusion, effective protection, in this field too as in many other cases, must
necessarily be the result of a twofold process whose basic steps are: the careful design
and construction of the protective equipment vis-A-vis the hazards to be faced and
systematic operator training.
In this particular instance, we believe that the outfit being considered can afford
adequate protection, even in the most difficult situations, to the people in charge of
fire fighting operations, shielding the different regions of the body in relation to their
importance.
RÉSUMÉ. L'incendie de
forêt accident non rare dans les pays méditerranéens, présente des caractéristiques
particulières qui conditionnent les types de risque qui sont liès, dont le principal est
naturellement la brûlure. Les accidents les plus fréquents, selon les staÂstiques, sont
causés par des feux imprévus ou par le changement brutal du front de l'incendie
aux abords duquel opèrent les équipes de se(ours. La température de la source de
chaleur en de tels cas atteint des valeurs maximales que l'on peut estimer à 500 degrés
et le temps d'action du secouriste est en général de 20 à 30 secondes. On a donc
étudié un vêtement de protection a~)te à prévenir les risques de brûlures ou a en
réduire les gravités, en tenant compte des conditions du milieu et du climat où
l'incendie se propage et des facteurs physiques qui le caractérisent. Les qualités
spécifiques que l'on demande à ce type de vêtement sont les suivantes:
- facile à endosser et commode pendant tout le temps que le secouriste le porte
- il doit protéger toutes les parties du corps (~t en particulier celles les plus
exposées, le visage, les mains, le périnée, etc.
- protéger pendant suffisamment longtemps pour garantir le passage du front du feu aux
températures évaluées
- qu'il ne permette pas l'accumulation de chaleur
- qu'il enregistre graduellement l'augmentaticn thermique de façon à prévenir le
secouriste du danger imminent.
|