Melting Pot Wiki - User contributions [en]

Index

2008-03-03T16:41:56Z

MikeAurelius:

==Quick Index Page==

Contributors, add your link alphabetically.
* [[Borosilicate]]
* [[Chinex]]
* [[Frit]]
* [[Glasshole]]
* [[GTT Lynx]]
* [[GTT Phantom]]
* [[Kilnbuilding; Safety Controller Layout]]
* [[NOX hazards to the glassworker]]
* [[Pre-mix torch]]
* [[powder]]
* [[Sepulworld]]
* [[Soft glass]]
* [[Surface mix torch]]
* [[Triple Blown]]
* [[Triple Mix]]
* [[Vin-pin]]
* [[Visible Light Hazards]]

Index

2008-03-03T16:40:52Z

MikeAurelius:

==Quick Index Page==

Contributors, add your link alphabetically.
* [[Borosilicate]]
* [[Chinex]]
* [[Frit]]
* [[Glasshole]]
* [[GTT Lynx]]
* [[GTT Phantom]]
* [[Kilnbuilding; Safety Controller Layout]]
* [[NOX Hazards to the Glassworker]]
* [[Pre-mix torch]]
* [[powder]]
* [[Sepulworld]]
* [[Soft glass]]
* [[Surface mix torch]]
* [[Triple Blown]]
* [[Triple Mix]]
* [[Vin-pin]]
* [[Visible Light Hazards]]

NOX hazards to the glassworker

2008-03-03T16:39:43Z

MikeAurelius:

Many people, some of them fairly influential in the glass-working field, have publicly stated that it is difficult, if not impossible to work in a properly ventilated public studio. These same people have said that it is “OK” to open some windows and doors and use some box fans to move air around, but to also take frequent breaks. As this paper will show, this thinking is short sighted, and ultimately dangerous to the uninformed (especially new students).

This failure to take the initiative in presenting a united front for studio safety has led me to research one of the principle reasons glass-working studios MUST properly ventilate their work areas. That reason is NOx. The chief “bad actor” (as Stan Wolfersberger calls it) of the NOx family is NO2, nitrogen dioxide.

NO2 is one of the principle components of air pollution, shown visibly in the air as a brown cloud hanging over large cities. It is caused in part by internal combustion engines, coal burning plants, and other high temperature open flame sources.

Glass-workers are exposed to NO2 on a daily basis, and most, if not all, are not aware of the major problems that NO2 can cause.

NO2 is a toxic poison. Symptoms of poisoning can take several hours to appear, and the dosage is surprising low in order to inhale a potentially fatal dosage. Dosages as low as 4 parts per million (ppm) anesthetize the nose resulting in the loss of the ability to smell, which can easily result in overexposure.

According to the MSDS, NO2 is highly toxic by inhalation, and inhalation may be fatal. It is corrosive in its liquid form, or when combined with mucus or tears and forms nitric acid. It is considered a severe respiratory irritant. Permissible exposure level is 5 ppm. Contact with liquid causes severe eye damage and contact lenses must not be worn when exposed to NO2.

The fatal doses of NO2 are as follows:
Lethal concentration, 50% population kill: 88 ppm over 4 hours (rat)
Lethal concentration, 50% population kill: 30 ppm over 1 hour (gerbil)
Lethal concentration, 50% population kill: 1000 ppm over 10 minutes (mouse)
Lowest published lethal concentration: 200 ppm in 1 hour (human)

The MSDS recommends safety glasses and good ventilation. Use in a fume hood.

There is a latency period (delay) before symptoms may develop of anywhere from 2 to 48 hours. The early symptoms may manifest in any of the following:
Dyspnea
Cough
Chest pain
Clinical manifestations of noncardiogenic pulmonary edema

2 to 6 weeks after exposure the following symptoms may also develop:

Bronchiolitis obliterans, manifested as fever, cough, and dyspnea
Diffuse reticulonodular or miliary pattern on chest x-ray

Initial physical impact may be mild, but can progress over 72 hours to be life-threatening:

Pulmonary symptoms are the most common manifestation of nitrogen dioxide toxicity.
Cough
Dyspnea
Chest tightness
Choking
Wheezing
Chest pain
Rales
Rhonchi
Decreased breath sounds
Stridor

Other acute symptoms
Light-headedness
Loss of consciousness
Restlessness
Agitation
Confusion
Irritation of mucous membranes, including the eyes
Conjunctival infection
Weakness
Fatigue
Nausea
Abdominal pain

Delayed symptoms
Tachypnea
Headache
Fever, chills
Insomnia
Myalgias
Hemoptysis
Palpitations
Cyanosis
Coma

Now, granted, these are wost-case outcomes of high doses of NO2, however, any of these symptoms may develop, especially if the patient has a pre-existing medical condition, such as one that is pulmonary-related.

NIOSH has placed a 1 ppm limit of exposure, with 20 ppm as immediately dangerous to life and health.

ACGIH places a 3 ppm limit over time, and a 5 ppm limit on short term exposure.

Every source available states that proper ventilation and protective gear are required by anyone exposed to even low levels (under 2 ppm) of NO2.

Sources:
WebMedicine - part of WebMD
University of Kansas, Poison Control Center
NIOSH - National Institute for Occupational Safety and Health
OSHA - Occupational Safety and Health Administration

Index

2007-11-21T14:58:20Z

MikeAurelius:

==Quick Index Page==

Contributors, add your link alphabetically.
* [[Borosilicate]]
* [[Chinex]]
* [[Frit]]
* [[Glasshole]]
* [[GTT Lynx]]
* [[GTT Phantom]]
* [[Kilnbuilding; Safety Controller Layout]]
* [[Pre-mix torch]]
* [[powder]]
* [[Sepulworld]]
* [[Soft glass]]
* [[Surface mix torch]]
* [[Triple Blown]]
* [[Triple Mix]]
* [[Vin-pin]]
* [[Visible Light Hazards]]

Visible Light Hazards

2007-11-21T14:55:52Z

MikeAurelius: A review of the hazards to the glassworker from visible light

'''Introduction'''

Most glass workers are all familiar with sodium flare, that annoying ball of yellow light that occurs when glass, most notably soft glass, is exposed to flame. As the glass molecules heat up, sodium in the glass is burned, creating a sodium flare. Didymium and ACE (Amethyst Color Enhancement, trademark of Schott Glass Technologies) filters (sold under a variety of trade names by various manufacturers) all remove sodium flare from the wearer’s vision.

While the hazards of UV radiation (UVR) to the eye are well known by most individuals, the issue of High Energy Visible (HEV) light and High Intensity Visible (HIV) light are not. Since most of the work that glass workers perform does not generate UVR, the main discussion points of this article will focus on the HEV and HIV hazards.

HEV is defined as visible light radiation from 380 nm to 530 nm in the visible light spectrum. In terms of apparent color, these wavelengths correspond to violet to blue-green. As a reference point, sodium flare is at 575 nm.

For the purposes of this article, HIV is defined as luminescence in excess of 10,000 lumens. 1 lumen is the luminescence of 1 candle. A 100 watt light bulb emits approximately 120 lumens. Sunlight on a white sand beach can range from 8,000 to 10,000 lumens. Fresh snow on a sunny day can have a luminescence as high as 30,000 lumens.

'''The Process of Vision'''

Both visible and “invisible” (UVR and IR [Infrared Radiation]) light consists of energy in the form of photons. As photons strike the retina, the physical force of the photons is converted into chemical energy producing electrical impulses perceived by the brain as “light”. This chemical process uses potassium and sodium ions and sensory cells in the form of rods and cones.

'''Night Vision Problems'''

Rod cells are highly sensitive to light, on the order of 4 magnitudes (10,000 times) greater than cone cells.

In low light conditions, a chemical called “visual purple” (rhodopsin) allows the rods to be particularly sensitive to faint sources of light. Visual purple is a combination of a protein called opsin and a light sensitive substance called retinene. Rod cells are elongated cylinders which contain about 2,000 stacked discs. Within each disc are upwards of 100 million components of visual purple.

Visual purple is extremely reactive to light. Even small amounts of light will cause the “bleaching” of visual purple. During HIV conditions, visual purple is consumed much faster than it can be produced by the body. When luminance conditions decrease rapidly from HIV levels to relative darkness, the eye is left without a reserve of visual purple. A light adapted eye (one that has been exposed to HIV conditions) will be less sensitive to dark conditions by as much as 10,000 times as an eye that has had at least 40 minutes of exposure to dark conditions.

Prolonged unfiltered exposure to HIV increases the time cycle of visual purple replenishment and can affect an individual’s ability to adapt to low light levels. Individuals who spend long periods of time exposed to HIV are particularly susceptible to longer adaptation times when moving to relative dark conditions.

'''Glare Problems'''

Too much light, called glare, can cause discomfort or even disrupt vision. Glare can be broken down into two categories: discomfort glare and disabling glare.

Discomfort glare generally does not degrade vision; however, it is certainly distracting and is capable of causing pain and/or eye fatigue. Discomfort glare commonly results from one of two conditions – excessive amounts of illumination and/or reflections in the visual field. Excessive lighting causes actual pain and discomfort. Surroundings such as sand, water or polished surfaces can also produce discomfort glare.

Eye discomfort is poorly understood since the retina has no pain receptors, there is evidence that suggests that the discomfort felt in bright light is triggered by the constriction (or size decrease) of the pupil. If you have ever forgotten to wear sunglasses on a sunny day, you know the feeling! During and after prolonged exposure to uncomfortably bright conditions, symptoms such as headache, eye and overall fatigue are common. Individuals with light colored eyes are generally more susceptible to the symptoms than individuals with dark colored eyes.

Distracting glare is a form of discomfort glare best noted as the reflection from your eyeglass lens. While such reflections do not decrease visual acuity, they do distract the visual system and may cause passing areas of decreased perception in the visual field. For example, the headlights of a passing car can create glare in the form of “ghost images”.

Disabling glare occurs when a light source within the field of view has luminance that is disproportional to the other objects being viewed. The source of the glare may be direct or indirect. A perfect example of this is an object passing close to the viewed sun. The direct luminance of the sun is far brighter than any other object in the sky, obscuring anything near it.

Blinding glare is a form of disabling glare, and occurs when glare is severe enough to prevent useful vision of objects within the field of view. A good example is the reflection of sunlight from a body of water.

One consequence of glare is decreased contrast sensitivity. A 1995 study conducted by an automobile insurance company revealed that driver reaction times were slower in the presence of glare.

'''AMD'''

Age-related Macular Degeneration (AMD) is the result of photochemical damage affecting the macula, the central vision portion of the retina. It is the leading cause of blindness in people over the age of 50. The visual effect of AMD can be described as looking at a clock and being able to see the numbers but not the hands. One person in six, by age 55, will develop AMD.

Extended exposure to HEV and HIV may increase the development of AMD. UVR, HEV and HIV have been shown to have a major impact on photoreceptor and retinal pigment epithelium (RPE) cell function, inducing photochemical damage and cell death in the rods and cones. This may lead to early onset of AMD.

'''Conclusions'''

Proper filter eyewear is an absolute requirement for anyone working with hot glass.

Clear lenses do not provide proper filtration of UV, HEV or HIV wavelengths and should not be worn during any hot glass operation.

Didymium and ACE (Amethyst Color Enhancement) filters by themselves provide safe filtration for soft glass workers but should never be used by borosilicate glass workers without additional visible light filters. If you have light colored eyes, you may wish to consider adding additional filtration depending on your personal sensitivity to bright light. Additional filtration may be required by anyone working with glass that contains silver additives or any other material that create bright visible light flares.

Individuals working borosilicate glass must always wear a shaded lens that provides a maximum of 10 to 12 percent visible light at the HEV wavelengths (which translates to a welding shade 3.0). Darker shades must be worn when working with glass that generates very bright visible light flares, such as quartz, or when working with metals such as silver or gold.

Ensure that your eyewear is providing proper filtration. Your supplier should be able to provide a transmission graph showing what your eyewear transmits at specific wavelengths.

'''References'''

Pete Hanlin, ABOM, LDO “The effects of Visible light and UVR upon the visual system”

Algvere, Marshall, Seregard “Age-related maculopathy and the impact of blue light hazard”

Carol Dykas, LO ABOC, NCLC “How to protect patients from harmful sunlight”

Meyers, Ostrovsky, Bonner “A model of spectral filtering to reduce photochemical damage in age-related macular degeneration”

Marco Zarbin, MD, PhD, FACS “Age-related macular degeneration update: a review of pathogenesis, clinical findings and treatment”

J.M. Gallas, PhD “Eye protection from sunlight damage and vision performance with melanin lenses”

Copyright © 2007 by Michael Aurelius, all rights reserved. (copy for your own use freely, but please leave this copyright notice intact if you pass it on to others)