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Hydrazine: what to expect with the changes in the standard?
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Hydrazine: what to expect with the changes in the standard?

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Reactive in synthesis, hydrazine was the first jet propellant and owes its glory to the space adventure but it is a very toxic substance!

That's why the European Union has lowered this threshold from 0.1 to 0.01 ppm following the European Directive 2017/2398. This change - applied since January 17, 2020 - was recently included in the Decree No. 2020-1546 of December 9, 2020. This decree sets new occupational exposure limit values for certain chemical agents.

We thank ArianeGroup for the use of the Ariane rocket launch photos.

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What is hydrazine?

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What is hydrazine?
Diagram of the hydrazine molecule

Hydrazine with official name diazane, is a colorless liquid chemical compound with chemical formula N₂H₄. It has a pungent odor formed of hydrogen and nitrogen, reminiscent of ammonia.

A highly toxic, flammable and explosive substance, hydrazine is a high energy substance. Unstable from 50°C (explosion), hydrazine spontaneously oxidizes in air at room temperature (explosion). Under the action of sunlight, hydrazine decomposes into diazote and dihydrogen.
Vapour concentrations in air above 4% are explosive (38% for the concentration in nitrogen). Hydrazine vapors can explode on contact with flames or sparks.

The effects on humans are inflammation and burns on contact with the eyes and skin, even blindness. Ingestion, even for a short time, can attack the nervous system and cause death, while repeated contact can cause liver and kidney damage.

Uses of hydrazine

Uses of hydrazine
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Uses of hydrazine
Uses of hydrazine

Despite these highly harmful effects on humans, hydrazine is used in many processes: 260,000 tons/year are produced!

Most of this production is used as a foaming agent for the production of expanded polymers. The rest of this production is distributed in different sectors such as organic chemistry for the synthesis of drugs or inorganic chemistry for the production of the explosive agent for the inflation of "airbags" (safety airbags): sodium azodide.

In addition, a technique using hydrazine deposits on semiconductors has been recently experimented, with a possible application to the fabrication of thin-film transistors used for liquid crystal displays.

Hydrazine in a 70% solution with 30% water is used to power the EPU (emergency power unit) on the General Dynamics F-16 Falcon fighter aircraft.

In military use, a hydrazine derivative, asymmetric dimethylhydrazine (UDMH), combined with ammonium nitrate is the basic ingredient of astrolite, an extremely powerful explosive invented in the 1960s.

However, it is best known as a rocket engine fuel: it is used in low-thrust thrusters, such as those used for satellite and rocket attitude control.

"Hydrazine was first used as a rocket fuel in World War II for Messerschmitt Me 163 aircraft (the first rocket plane), under the name B-Stoff (actually hydrazine hydrate). This B-Stoff was mixed with methanol (M-Stoff) to give C-Stoff, which was used as a fuel with T-Stoff, a hydrogen peroxide concentrate, used as an oxidizer on contact with which it spontaneously ignited in a very energetic reaction.

Today, hydrazine is generally used alone as a monergol in low-thrust (but high-precision) engines for orbital positioning of satellites and space probes; in this case, the thrust is provided by catalytic decomposition of hydrazine and not by combustion.

This decomposition is triggered in a few milliseconds and allows to dose the thrust in a very precise way. These reactions are very exothermic (the catalyst in the chamber can reach 800°C in a few milliseconds), and produce a large volume of hot gas from a small volume of liquid hydrazine, making it a good propellant for space propulsion. "

Source: from Wikipedia

The Evolution of the Hydrazine Toxicity Standard

The technologies used to detect Hydrazine contents are numerous:

Mass spectrometry
Chromatography
Electrochemical cell
Colorimetry...
Until the end of 2019, the toxicity of Hydrazine has been stopped on a basis of VME = 0.1 ppm. To detect these low levels, industrial stakeholders use fixed or portable gas detectors with electrochemical cells. The other technique is the colorimetric detection in tube or paper.

From January 17, 2020, the European Union has lowered this VME threshold to 0.01 ppm, according to the European Directive 2017/2398

 

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VLEP Hydrazine
Gas Guide
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Gas Guide
Gas Guide

With this guide, you will find the essential information you need to know about the gases you encounter every day: their identification, their chemical and physical properties, the flammability limits and the occupational exposure limits. You will also find their descriptions, the most common uses, as well as the hazard and safety phrases.

In order to save you time, we also offer you a selection of equipment that protects you or alerts you to the presence of this gas!

The impacts of this new directive on gas detection

Today, manufacturers who need to monitor the presence of hydrazine in storage or in the process are faced with a problem where electrochemical detection, which is inexpensive and very reliable, is no longer feasible. Indeed, the precision thresholds are no longer in phase with this technology and the spectrometry or chromatography technologies remain very expensive.

To meet this regulatory constraint without incurring large investments, the only feasible technology is paper colorimetry*. However, there remains a constraint which is not the least important because these devices are not certified ATEX (for these zones, there are other technical solutions).

This technological and normative watch imposes to the industrialists to prepare their future with standards in constant evolution which imposes us to be vigilant as for the technical solutions to be proposed.
*Principle of colorimetry: after sampling the gas effluent, by an internal pump, the sample passes through a paper tape soaked in a reagent specific to the gas to be detected (target gas). When the gas comes into contact with the paper ribbon, a chemical reaction takes place and a colored imprint appears on the paper. This imprint is then reflected or crossed by an optical beam which according to the intensity of the task will define a concentration of gas in ppm or ppb. This colorimetric principle is very reliable because unlike electrochemistry there is very little cross interference between gases.

 

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What equipment?

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SPM FLEX et Chemcassette
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SPM FLEX

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Détecteur monogaz X-AM 5100
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X-AM 5100