The case for studio ventilation

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
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