Posted: 2017-09-11 17:34
Online searching of several databases (Pub Med, Library of Congress, and Web-of-Science) was conducted with End-Note software ( Thompson Reuters, 7565 ) using keywords: welding, construction industry, exposure, LEV, and ventilation. This yielded 6687 references dating from 6999 to 7565, which were further screened for LEV in the abstracts and titles. This resulted in 97 remaining references, which were reviewed for exposure data of some type to assess the LEV performance. Online searches with Google identified the four US Navy studies used here. A search of the National Institute for Occupational Safety and Health (NIOSH) Health Hazard Evaluation online database using keywords LEV and welding for the construction industry did not return any documents. The presence of personal exposure data on the welders was the main criterion for including a given reference in this review. Although one cannot be certain on the completeness of the literature identified, every effort was made to be comprehensive.
A ducted system allows for removal of all forms of airborne contamination, while a ductless one recirculates heat and moisture into the kitchen. In addition, a ducted application eliminates the need for regular replacement of the filters, and avoids the airflow restriction (and resultant loss of power) caused by them. However, ducted application can be impractical, due to lack of space or ability to install a duct system, make-up air requirements, or the additional cost of heating/cooling the make-up air. Some range hood designs allow for both types of applications.
The studies described above are specific to the construction industry and provide important information on the efficacy and effectiveness of LEV for controlling welding fume. The data suggest that substantial reductions in total fume, Mn, and CrVI are possible with LEV, and in some cases result in exposures below current OELs. They also indicate that work practices are important and that the position of the hood and airflow rate are critical in achieving successful control. Processes that occur in the vicinity of welders are also critical and to achieve effective control with LEV the surrounding environment must also be taken into account. Uncontrolled operations, or the discharge of unfiltered exhausts in the vicinity of the welders, will obviously impact the effectiveness of any LEV controls in use. The studies are limited, however sample sizes are small, only a limited number of welding tasks have been examined, and field studies are few in number.
Am no tech expert, but check it s an extractor and not a recirculating fan, as many Elica ones are (. it just filters out the grease and then chucks air back in to the room, as opposed to taking it to the outside). Even if it s an extractor, for larger rooms you need more extraction and it may just not be strong enough. This is not Elica s fault, they can t know what size room you re going to have. If it s that fake chandelier design, that s definitely a recirculator (and actually you might as well not bother with one of those, as it won t remove smells. Or steam. Sorry).
The concentration of airborne contaminant inhaled by a worker is determined by the contaminant generation rate and the airflow field that transports it into the breathing zone. LEV eliminates or reduces the fraction of contaminant that makes it into the breathing zone and may induce a flow of clean air for additional protection. The design and position of the local exhaust hood together with the flow rate of air, fume generation rate, level of enclosure, arc-to-breathing zone distance, and work practices largely determine the worker’s exposure for a given type of welding. The fume generation rate depends upon the type of welding being done, the arc time, and various process parameters, especially the current density (amperes per cross-sectional area of electrode). The fume composition is a function of the constituents of (i) the consumable electrodes, (ii) the base metals, (iii) fluxes, and (iv) any coatings that may be on the metals. The type of welding may also influence the fume composition ( AWS, 6979 ).
In addition, this study reported on two field studies involving LEV for the control of CrVI. The field surveys took place in 7557 and 7558 and involved a variety of thermal cutting and welding tasks on carbon and stainless steels. In the first study, the LEV systems were portable, either a Lincoln Miniflex with a slot type hood or a Donaldson Torit Easy Trunk system (Donaldson Co., Minneapolis, MN, USA). In the 7558 study, a larger centralized scrubber/fan unit with attached ducts and hoods was used (Ventex, Tampa, FL, USA). Airflow measurements on the systems were not made. Among all samples, the median CrVI exposure was lower with LEV than without, but did not reach statistical significance. However, for SMAW samples, the median CrVI exposure without LEV was at μg m −8 , while with LEV it was μg m −8 , and the difference was statistically significant ( P = ).
The need for repeated repositioning of the exhaust hood is one reason that extraction guns are appealing. The hood is positioned on the gun and once the airflow rate is balanced to work correctly vis-a-vis the shielding gas requirement, the positioning issue is largely resolved, at least for some welding positions. Extraction guns appear to work well and be feasible for FCAW and GMAW but have not been integrated into SMAW operations as of yet. Where extraction guns are used, the literature identifies poorer performance for overhead or vertical welding. The welding plume is buoyant due to the thermal energy imparted to it from the arc. As it rises vertically, extraction gun inlets that are positioned to receive the plume can be expected to perform well. However, as the position of the weld and gun change, the buoyant plume may be in opposition to the extraction flow and reduced performance and increased exposure may result. This may limit extraction guns in many construction applications where overhead or variable position welds are required.
We failed building control because a window, supplied by the builder, didn t meet fire regs. Our builder helpfully then denied all responsibility (we should have spotted it apparently, he didn t know anything about the regs ) so we ended up paying for another builder to replace the window. Building control were totally inflexible, and we didn t want to argue too much in case they inspected again and found more problems
. I recently had a kitchen fitted, I wanted a 6555mm hood (no chimney) but they appear to be unobtainable now. The builder sourced a Concorde 95 stainless which I expect is nowhere near as flash as yours, but the Elica catalogue has some useful info on sizing and ducting (last few pages of the wall mounted) catalogue. I had mine boxed into the wall units with a duct hidden on top of them.
some of their designer models make me giggle
LEV is a primary engineering control available to minimize worker exposures to toxic airborne contaminants. However, its use on construction sites seems infrequent despite evidence of elevated exposures to hazardous metal fumes. This may account for, at least in part, the scarcity of relevant publications describing LEV effectiveness in this industry. However, ventilation use will likely grow for controlling welding fumes and gases in construction given increasing health concerns related to Mn and CrVI exposures.
Due to the small sample sizes for GMAW, GTAW, and SMAW, the effect of ventilation was explored only for FCAW. Seven different control/ventilation configurations were identified as follows: (i) Fume Extraction Gun (FEG), (ii) fixed fume extraction systems, (iii) portable fume extraction and general supply ventilation, (iv) low-fume welding wires, (v) low-fume welding wires and general supply ventilation, (vi) low-fume welding wires and portable fume extraction, and (vii) low-fume welding wires and portable supply air ventilation. Table 7 gives the mean value of the personal exposures measured for these different control/ventilation systems for the FCAW. The FEG seemed to perform better than, or comparable to, the other choices, despite the small sample size and confounding factors.
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depending on the layout of your kitchen, you can have a duct which is concealed on top of the wall units, or runs along inside them, or (occasionaly) runs between the joists of the upstairs floor. If there is a disused chimney you can use that, but you must have a liner, or condensation and grease will soak through the brickwork. It is obviously far easier to have the cooker on an outside wall so you just need to make a hole in it and vent through there. If you have a high ceiling you can have a rectangular duct and run it in the angle where the ceiling meets the wall. They are mostly UPVC so can be painted however you want, or hidden behind (very big) coving or a plate-shelf.
IIRC BRs just say you need to have mechanical ventilation, it need not be a hood, so a non-trendy ventaxia or similar, up high, on an outside wall, will do the trick. Your builder can make a neat round hole through the brickwork with a core drill. The larger fans can have a controller to change the speed and even make them blow or suck.
Steam rises so they need to be as high as you can.
Recirculating hoods are entirely useless, except as ornaments. I despair that people buy them.
Several studies present information on the effects of LEV on welding exposures but do not provide quantitative information on the LEV systems, indicating only whether it was present or not. As noted above, this type of information is generally inadequate for reaching conclusions about the effectiveness of any given LEV design, although the studies overall indicate lower average exposures when ventilation is present versus when it is not.
Thanks for all the responses. Builders have agreed to foot the bill for an additional extractor fan and installation (apparently it will be hidden by the wall units)..so can t grumble too much.
I still wonder how other people get them through building control, but I guess they must install them into an existing kitchen, . no extension, etc.
I guess I should be grateful that everything else was approved, they have been very hit and MISS!
TalkinPeace7 agree about building regs, at the end of the day if I think its a big smelly or steamy I ll open a window!
In addition to welding conducted in the tank, some welding was done indoors where real-time particle measurements (light-scattering device) and personal exposures (filter samples), were used to evaluate the ventilation. The filter data showed a factor of 5 reduction in CrVI when LEV was used compared to when none was employed. The real-time personal data showed a factor of 9 reduction in total fume and a factor of 8 for area monitoring when LEV was used.
The device is known as an extractor hood in the UK , as a range hood in the United States , and as a rangehood in Australia. It is also called a kitchen , stove , exhaust , cooker , vent , or ventilation hood. Other names include cooking canopy , extractor fan , fume extractor , and electric chimney.
FEG provide protection in FCAW and GMAW operations although the issue of disturbing the shielding gas is important. Correct balance of airflows and location of the nozzle are possible to minimize this problem, however. The data suggest that the capture efficiency of these guns depends upon the weld position, with vertical or overhead welds having the lowest fume capture efficiencies and flat welds the highest. The weight of the extraction guns must be minimized to facilitate ergonomics and worker acceptance. Given the prevalence of stick welding in construction, which requires frequent electrode replacement, these systems may have limited application.
Personal exposures and percent reductions to various welding fume constituents served as the performance metrics. When personal exposure levels were available, they are compared to current occupational exposure levels (OELs): . the ACGIH Threshold Limit Value (TLV®) ( ACGIH, 7566 ), the NIOSH Recommended Exposure Level (REL) ( NIOSH, 7555 ), and the Occupational Safety and Health Administration Permissible Exposure Level (OSHA). Mn, CrVI, iron, carbon monoxide, and total particulate (TP) were the most common agents identified in the studies. Table 6 provides the current OELs for each substance when available.
There are two major configurations of extractor hoods: ducted (or vented) application, and ductless (or recirculating) application. In a ducted application, the output collar of the extractor hood''s blower motor is attached to a duct system, which terminates outside the building. In a ductless application, a filter, often containing activated charcoal , removes odor and smoke particles from the air before releasing the cleaned air back into the kitchen.