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(SILENCE)

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VOICE-OVER: Welcome to one
of ConsExpo Web's online tutorials.

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This video will give you insight
into the exposure estimated...

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by the spray models available
in ConsExpo Web.

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Many consumer products are applied
by spraying...

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and there is an increasing trend
of spray applications.

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Examples are air fresheners, deodorants,
fly sprays, adhesives and so on.

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Spraying of those products
leads to the release of a substance...

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as an aerosol into the air
or onto a surface...

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depending on the purpose
of the application.

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The release of the substance of interest
from an aerosol into the air...

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can be modelled using the spray models
in ConsExpo Web.

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Two models are currently available.

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A low-tier model describing the instant
release of a substance into the air...

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and a more sophisticated model
called the spray model.

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The model's methodology is presented
in a real-life scenario...

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of a person using an air freshener
in their living room.

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The residential setting consists of a room
in which a person uses the spray.

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The room can be described by providing
the room volume and room height.

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The user of the spray product can be
described by providing information...

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on body weight and inhalation rate.

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In this example, the user is an adult.

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Once you have entered information
about the room and the user...

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the next inputs relate
to the aerosol and its constituents.

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Next, describe the behaviour of the sprayed
aerosols to a number of model parameters.

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The duration of spraying.

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The mass generation rate...

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describing the amount of product
released per unit of time.

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The former two combined
provide the total released amount.

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The airborne fraction...

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which is the fraction of aerosols remaining
airborne and thus available for inhalation.

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The particle size distribution of the aerosols
and how they disperse across the room.

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And finally, the removal of aerosols
from the air...

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by gravitational settling
and ventilation of the room.

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The physics of release and dispersion
are quite complex.

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The instant release model simplifies
the release and behaviour...

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of the spray and the substance.

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It makes no allowance for the fact
that some substances...

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are released as aerosols or vapours.

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Furthermore, it does not take into account...

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whether the product is used
on a surface or not...

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which may affect the airborne fraction.

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Instead, it assumes
that a specified product amount...

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is instantaneously released into the air.

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This model provides a conservative
estimate of the concentration in the air...

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and is used for situations where:

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a quick conservative estimate
of the exposure is desired...

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information on the spray application
and its use are lacking...

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volatile substances with a vapour pressure
above 1 Pa are released...

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by the spray application.

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Such volatile substances evaporate almost
immediately due to the high release area.

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If additional product data are available
and refinement is needed...

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the spray model can be used.

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Similar to the first-tier approach,
you need to enter the duration of spraying...

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mass generation rate and exposure
duration to describe the product use.

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Additional input is needed to describe
the airborne fraction...

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and particle size distribution.

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The airborne fraction describes the amount
of spray that is released into the air.

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This depends on the direction of the spray
and type of spray product...

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meaning for example a trigger spray
or aerosol.

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The particle size distribution
is an important parameter...

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that determines what happens to the spray.

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Based on diameter size...

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the model simulates gravitational
settling within a room.

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This is used to estimate the duration
that spray will be available in the air.

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The smaller the spray amount, the longer
it floats in the air and can be inhaled.

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Besides gravitational settling...

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the model assumes an even distribution
of aerosols across the room.

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In some cases,
this assumption is not justified.

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When sprayed towards a person...

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you can assume that there is an initial cloud
surrounding the breathing zone.

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The model crudely splits the first moments
of release into the cloud...

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after which immediate dispersion
into the room is considered.

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A second way of removing spray
is by ventilation.

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This works in a similar way
across inhalation models...

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and assumes a certain exchange
with fresh air.

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When using ConsExpo Web...

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the desired information
is to be provided by the user.

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We use the example of an air freshener
to show the functionality of the model.

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Please note the insert fields
for the particle size distribution...

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and the option to provide raw data.

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We run through the input fields
providing information on spray duration...

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mass generation rate, airborne fraction
and particle size distribution...

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which requires the median particle size
and coefficient of variation.

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Furthermore, we wish to highlight the
requested cut-off diameter for inhalation.

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This means that smaller aerosols
are available for inhalation...

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but bigger aerosols only for oral exposure.

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Note that bigger aerosols
will drop to the floor rapidly...

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but some may still end up
in the nasal and oral cavities...

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where they are assumed to be ingested.

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If you are interested
in the integrated exposure to a spray...

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you need to tick the box marked 'include
oral non-respirable material exposure'.

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After completing the insert fields,
the model can be simulated.

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Running the spray model
with the example in mind...

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yields results for the concentrations
in the air, exposure estimates...

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and graphs of the exposure event
and how it evolves over time...

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defined by the exposure duration.

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We hope the tutorial has helped you
to familiarise yourself with ConsExpo Web.

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Our support does not end here.

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Visit the ConsExpo website
for help pages...

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that provide information on ConsExpo Web
and a user manual.

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You can also access the 'i' and '?' icons
within the software...

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which are there to give you extra help
when needed.

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If you still have questions
or need assistance...

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please contact us at consexpo@rivm.nl.

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(SILENCE)