Hi everybody,

I'm investigating (is it the right forum session, isn't it?) a fire that broke out from inside a wall (the insulating foam caught fire due the heat coming from the pipe of a exhaust flue of a fireplace).

I'm wondering if it's possible to estimate the flux rate of gas (essentially CO) out coming from the wall.

I know which are the wall layers:

mortar 1 cm

brick 20 cm

polyester 2 cm

Unfortunately I know only “water vapor permeability” of these materials.

Do you think I can use the water vapor permeability to assess whether and how a gas (carbon monoxide) has gone through a wall?

Recalling the definition of 'resistance to water vapor μ

“The value μ of a material construction is a parameter, without dimension of the matter itself, which indicates how many times the building material is more insulating vapor, compared with a layer of still air of the same thickness.

The larger the parameter μ, the greater will be the impermeability to vapor of the material construction!”

I can use it to get an indication (or exact values, note the differential pressure) of a gas other than water vapor?

Here the wall values, with μ equal to:

mortar 38

brick 8

polyester 45

Using Fick's law - for one dimension - that ∂ c / ∂ t = - D ∂ ² c / ∂ x ² ; dimensionally

∂ c / ∂ t [kg / m³ / s] = - D [m · s] · ∂ ² c / ∂ x ² [kg / m³ / m²]

in steady state I can transform this one as:

0 = - D · ∂ ² c / ∂ x ² and integrating - K/D = ∂ c / ∂ x

but I can go further...

Any idea?

Thanks.

Andrea

I'm investigating (is it the right forum session, isn't it?) a fire that broke out from inside a wall (the insulating foam caught fire due the heat coming from the pipe of a exhaust flue of a fireplace).

I'm wondering if it's possible to estimate the flux rate of gas (essentially CO) out coming from the wall.

I know which are the wall layers:

mortar 1 cm

brick 20 cm

polyester 2 cm

Unfortunately I know only “water vapor permeability” of these materials.

Do you think I can use the water vapor permeability to assess whether and how a gas (carbon monoxide) has gone through a wall?

Recalling the definition of 'resistance to water vapor μ

“The value μ of a material construction is a parameter, without dimension of the matter itself, which indicates how many times the building material is more insulating vapor, compared with a layer of still air of the same thickness.

The larger the parameter μ, the greater will be the impermeability to vapor of the material construction!”

I can use it to get an indication (or exact values, note the differential pressure) of a gas other than water vapor?

Here the wall values, with μ equal to:

mortar 38

brick 8

polyester 45

Using Fick's law - for one dimension - that ∂ c / ∂ t = - D ∂ ² c / ∂ x ² ; dimensionally

∂ c / ∂ t [kg / m³ / s] = - D [m · s] · ∂ ² c / ∂ x ² [kg / m³ / m²]

in steady state I can transform this one as:

0 = - D · ∂ ² c / ∂ x ² and integrating - K/D = ∂ c / ∂ x

but I can go further...

Any idea?

Thanks.

Andrea

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