We use a fume hood but we don't turn it on when weighing.  After weighing
it's left on for 10 minutes i.e. till someone remembers to turn it off.
This provides containment and a defined working area.  Whether extraction
contributes anything is a moot point.

With all weighing operations, especially lightweight dyes and other nastys,
there is no substitute for safe handling and no fume hood or other device is
going to make up for deficiencies of handling.

Andy Shand
----- Original Message -----
From: Histomail\ <histomail@netspace.net.au>
To: <Barbara.Davies@memhospcs.org>
Sent: Thursday, October 19, 2000 11:04 PM
Subject: Re: fume hood for balances


> Dear Barbara,
> your safety officer may have a valid point. We already know that some dyes
> are potentially carcinogenic eg. the Rosanilin derivatives, crystal violet
> etc.
> While the use of a fume cupboard may be very useful for extracting fumes,
> they interfere with both the operation and accuracy of the balance, unless
> the balance is enclosed such as your Mettler. The risk is in opening and
> transferring powdered dyes from the original container to the weighing
> vessel- I would make the following points:-
> 1) Always wear a surgical mask, gloves and apron when carrying out
weighing
> operations.
> 2) Never use plastic receptacles to transfer or weigh powders, as these
may
> have significant electrostatic charge, and disperse powder all over the
> place even microscopically.
> 3) If using an extraction device, position so that airflow does not overly
> affect performance of balance- the device must not be part of the
> construction of the bench. Sealing door slides on a balance are
recommended.
> 4) Ensure all equipment and bench is properly grounded.
> 5) All used equipment, vessels etc even if disposeable, should be placed
> directly into a bucket of cleaning agent (I use Domestos/soap solution) to
> wet the vessels etc. to prevent unwanted spread of powder during wash up
or
> disposal. Also makes washing up easier.
>
> Personal note:- I have used a small perspex box (2x2x2 ft) for weighing
> small volumes, the front of which is open , and the rear of which has a
> cut-out into which is connected a Phillips Air Purifier for asthmatics
> mounted on a foam pad - this is fitted both with and extraction filiter
> designed for dust and pollen, and also includes an electrostatic
> precipitator. This device is both transportable, and has minimal
> interference on the balance performance but is only suitable for masses
> 2-500g. for masses less than this a balance with closeable slides must be
> used.  Your local hanyman can knock one of these up for you in a few
moments
> for a minimal cost.
> I would make a final comment, some will say that only a fume cupboard is
> satisfactory, I must empasise that certification of fume cupboards is
> carried out when they are empty; and I must say that their performance can
> be vastly different with a bulky object placed inside them, and I suspect
> offer no advantage over our little home made box!! Besides fume cupboards
> are not designed to remove dust!!!
> Regards Mike Rentsch (Downunder)
>
>
>
>